The first thing you should do is post a thread like this to the iPad section. I'm too lazy to grab the link from my iPad2.
Tip, check the top apps every week or so to find the ones that are on sale. Apps on sale tend to sell very well and end up in the top 10.
Tip, play around with all the controls to find out all the nifty shortcuts. Double pressing home brings up the recently opened apps (useful for multitasking) but if you swipe to the left, you get brightness, volume and media controls.
Tip, most popular sites/channels/companies/etc have an app. Quick examples are eBay, Amazon, BBCi (player), even Westfield Shopping Center has an app.
Pro tip, there may be an app for "everything", but most of them suck. Trying to get a free app for a simple Magic the Gathering tool is nearly impossible.
Tip, most tools and games have a free "demo" version. Best example, object finding adventure games nearly all only have a couple rooms to find objects in then ask you to buy the full version unlock. Others just have a "lite" version and a full version in the app store.
Tip, 90% of flash based sites (e.g. Streaming sites) will not work with Safari. SkyFire has a way to stream those videos to you, but it's not perfect, and it's not free.
Tip, if you have a 3G version, get a data monitoring app to make sure you don't go over the limit. If you have a 3G iPad but no data plan yet, T-Mobile provide the cheapest data plan by far (£20 for 6 months unlimited, with fair usage policy of 5GB).
Tip, there are apps to play video files. You do have to use iTunes to transfer the movies into the app however.
Recommended apps from me, Skype (sucks, like on all iOS devices, but at least it works), IM+ (instant messaging, works with most networks), MyPad (FaceBook and Twitter), SkyFire (it's not free).
For jail breaking, there is a website that is easy to use. Go to the website, slide the slider, and you're jail broken (providing you're not above 4.3.3). I haven't made much use of it however, since the only tweaks that interest me are paid for.