5 main options (although nothing to stop you merging a few/the lot) as I see it assuming you are not going to say design websites or do SEO for people or some such (in which case you are more a business with a website), becoming a paid mod/contributor for a forum/site (more in line with a traditional job) or building up a proper service (it might not end up at that level and you might not wish it to but the words "the next" could well be thrown around).
The one who figures this out will probably make a good of money as well- many have come before you and many of those have had serious skills across a field or two and decent website building skills to back it* in addition to a lot of time.
You might also consider messing around on social networks and the likes of youtube (either in general or hoping to catch the eye of somewhere) and done properly there does seem to be something of a traffic payoff.
*know basic HTML, basic CSS and at least how to paste things together for php before heading into this (basic web design is not that hard and you can usually customise stuff with a bit of reading- right click and view source on every site you like the look of, realise stuff like "<?php include 'includes/nameofsomefile.html';?>" does for HTML what CSS does for making sites easier to manage). Some might say javascript as well but I would sooner say php- either way we have http://www.w3schools.com/ for this.
You can get away with far less and just install some standard web software like wordpress or something (do also note there are loads of premade blogs, code fragments (tables, email address hiding, page layouts) forums, photo galleries, email frontends, wikis, email database/mailing list software, file hosting methods........ all with nice licenses (GPL, apache and BSD are the main ones to look for and possibly creative commons depending on how "professional" you want to look) if you look hard enough but those that know those first three things have a serious headstart. The main problem with premade stuff is upgrading if you customise it (and you will want to customise it- speak to any web design about this if you like but prepared to dodge a thrown object) and to my mind security (I screw up it is on me but having to vet an entire piece of web software is a pain a doubly so if you are not a web programmer).
How to resize/convert an image goes without saying and how to do some video stuff helps as well.
In addition to this I suggest you learn a bit about DNS (a least what an aname and cname are). Along similar lines the one piece of advice above all others is register your domain with one company and host it with another even if they offer you an amazing deal to bundle both of them.
You can do very well for yourself using nothing but open source should you so desire so you can avoid springing for fancy CMS type things and indeed the offline site building/image editing tools.
If you are going to start dealing with companies brush up on some basic contract law and always do the research (depending on your outlook on life "trust but verify" or "assume they are taking the piss until you feel reasonably confident they are not). Wound into all this sometimes you can work it so you get free stuff from companies or someone that sells their products in exchange for a review and possibly a token sum on top of that. Unless you are doing comedy reviews or specialist stuff it gets tricky.
I am discounting things like paid surveys and such as they are pretty much all scams and if I had a gimmick with a chance of working (see something like that 1 million pixel advert site) my sharing it with people is obviously not going to happen.
1) Buy and sell junk (possibly even fix it/strip it for parts)- see how most shops work offline and repeat online at your favourite tat merchant (or several/your own site). Your main options (assuming you are not repairing things) are buy low and sell high (quite difficult unless you have a specialist area or wish to play importer- many will suffer a marginally higher price if it comes from within their country's borders or indeed you might see that importing still leaves some room for a decent margin) or buy a lot of tat and split it- I sell you my entire box of random electronics parts for $10 and you split it all up to some 100 items and sell them for $1 each (plus shipping and handling/postage and packaging of course- shipping is a big scam basically but people suffer it). Stripping things for parts works in a similar manner (a broken device is one thing but parts for it quite another and as parts are still likely to be cheaper than replacing it again they will suffer it). You should note though that the tax man might want to know about this if you are doing it as part of a business.
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Ignoring the parts/repair stuff above now we get into the area where you need some skills (writing/reviewing, being an artist of some form, being an scientist/engineer/tradesman of some form*) or funding to start it up and if possible a niche to go with it but unlike older media where people pretty much were locked into a thing when online people tend to come as long as it is worth coming so a nice is not all important and you can specialise within it if you want (for instance you are probably not going to be able to build up a forum to rival GBAtemp in an instant but if you say figured that GBAtemp's comedy section was a nice idea but otherwise not up to much you could start up JinTrigger's GBA, DS and Wii related comedy extravaganza and hopefully pull some readers there).
*remember this is the internet where one can be an astronaut that dabbles extremely successfully in the stock market at the same time as being a surgeon- the little observed corollary of that though is where in real life one tends to need a bit of paper or to have done something and been paid to do it for some years before claiming some mastery of a skill if you actually have the skill for some reason (and why not- university level educations, often from
actual universities, are available for free online) it is all good.
2) Simple google ads or equivalent- you basically get a bit of javascript or such to stick on your pages and advert companies send you money depending on views of them, clickthrough rates, eventual sales (if any) and so forth. Some sites will also share ad revenue (mainly video sites) but this is a slightly different matter. Unless you are very good at what you do (not to mention most of these are agreements along the lines of once you have earned..... then you will be paid) I would say you would be lucky to break even on hosting. Some are OK with this as you can turn around and stick "ran a website....." on your CV/resume which apparently counts for something (again if you have a nice site someone might knock on your email box to say do an article for us and we will pay you).
3) Proper adverts- you might negotiate with a company or a broker (brokers are in the same league as employment agencies for tendencies towards dick moves on all fronts) but they will say send you a picture and a link they want on the site (and where on the page and on what pages and......). This is reserved more for very big sites or specialist sites looking for specialist vendors (recall the be a scientist/engineer/tradesman thing from earlier).
By similar token you can also approach certain companies who will then offer checkout coupons or links you can add to videos for a discount/better trial or something.
4) Paywall/premium and I guess donations. If you think your content is worth it (hint- it probably is not- see even big news sites being lambasted when they try it) you can sit it behind a paywall so people pay to look at it. A bit more towards the nice side of things you can offer premium subscriptions (no ads, higher res videos, if you are a bastard you can offer a good site layout (all on one page where the other had to click through it), possibly premium content......).
It does not necessarily have to be your own content if you can say drum up a library of good info (see some datasheet/repair manual companies although there are just as many free ones).
Consider that small value sums of money are not that easy to send around and quite annoying for your and your would be clients even then... perhaps a premium rate text message type service or equivalent (several of the file hosters are doing it and I figure if those ringtone companies can afford to advertise on TV all the time...). Donations are an unreliable income source at the best of times but some can make them work, you can also mix this up and say sell branded or comical posters, tshirts and merchandise which are a bit more stable than straight up donations (some even manage to segway such things into kits (usual tech sites), books and more).
5) Service sites- people pay you to stick their site in a database for others to look at (see shoptemp as it currently stands and other directories) or pay you to put their articles up there (again not that likely to happen to you). Sometimes companies will pay you to run a forum for them (kick a cname from their domain to your forum or something) but in recent times that does not happen as they will instead opt to use a social network (apparently everybody has an account and are not hard to use for end user or admin) or a local version of their site. Tied to this are umbrella sites- see some of the webcomic "rings"/starter sites for instance but these are more of a long term play. Along similar lines I guess you have things like aggregation sites where many feeds come into one site- see some news sites, flash game sites, forum feed sites but these are usually a dance with the larger web hosting options (my single site per year hosting costs are almost exponentially higher than say the business I occasionally do work for that pays for a thousand sites from a service) not to mention dangerously close to spam (there are both legit and spam versions of these sorts of sites).
Equally most people that make these sorts of sites are coders or have them on hand (that usually wish to be paid) to make them.
