The only softmods to speak of are not very useful
I do not think profile sharing is up to much these days- here you would download a hacked profile and some XBLA games and DLC tied to it to play using said hacked profiles. People got banned and troubled by MS for it in the end hence my not being sure what goes.
PIRS installation- certain game of the year or equivalent discs (stuff like fallout GOTY and borderlands double pack) came with a type of DLC known as PIRS
Others run all from disc or merely came with download codes (many more including borderlands GOTY so make sure you get the double pack), this is fine for everyone to install and you can do it with injection using the USB drive (MS added the ability to save on USB which promptly got twisted to allow easier access to the hard drive) if you lack the ability to modify 360 hard drives (you can either use a drive transfer kit, a dedicated device like some from datel, a rebooter hacked 360 or pull it apart and it is just a laptop sata drive in the middle of it all)
Related to the PIRS stuff there is LIVE2CON and save editing. MS frowns upon save and profile editing and has for a long time so be sensible if you care about live or better just avoid it (you can edit profiles as well but MS really hates this and unless adding more gamerscore* for no reason and getting banned for it there is little to do other than maybe a tiny bit of customisation).
LIVE2CON... PIRS above is one of three types of files found on the 360 all of which are very closely related- LIVE is used by DLC, parts of the dashboard and XBLA and needs to be signed and authorised by MS to run unless you have a rebooter console, PIRS needs to be signed but can be installed by anyone and CON is for stuff like saves and profiles and can be signed by anyone with a key (which is many people and most tools with come with a key you can try). LIVE2CON exploits a bug which I am not sure still exists where smaller LIVE stuff could be turned into a CON file and some games would load it.
*I promised to try to not laugh at those that pursue achievements/trophies but those that "cheat" and get banned amuse me no end.
After this 360 hacking is broken into two main classes
1)DVD modding
360 games are sometimes region locked and DVD modding will have to adhere to this, no DLC or XBLA unless you buy it or use a method detailed up above, games will have to run from the DVD drive unless you use a DVD emulator, no hacked games, no extra niceties and no homebrew. Live should work still but people have been banned in the past although nobody has been banned for a couple of years now save for unrelated things and doing things like playing corrupt or AP2.5 laden games without relevant patching (AP2.5 has now been defeated for good where before you might have had to reburn every so often) and possibly playing games way before street date (although that is theoretically still doable, if very risky, as MS should have a hard time telling some if shop broke street date or you are playing a copy). With regards to bans we suggest a fatalistic attitude and to consider anything you get a bonus.
i) Classic DVD modding. You open the 360 up and flash a hacked firmware to the DVD drive, varies with model and generally the newer ones are harder to do and have more chance of needing some extra hardware to flash (not that expensive).
http://jungleflasher.../downloads.html has a nice tutorial that allows for far more detail than is viable here. General order of operations though is- obtain DVD key, build hacked firmware using DVD key and flash said new hacked firmware back to the drive. There are now standalone tools to flash DVD drives if you want but they cost a bit more than setting up a kit to use with a computer (or shipping it out to someone).
The discs will have to be dual layer (preferably verbatim ones) and MS made a new type of disc format called XDG3 which you will want a hacked DVD drive to burn- the models in question are a few from the ihas line*
*
http://c4evaspeaks.com/ is good to read as well as the above, do a page search for "Lite-On PC DVD Burner" to get a list of the DVD models you can use on the PC (the entry level ones are great drives, about the same price as normal DVD burners and can still be used as normal DVD burners after hacking.
ii) More recently we saw the likes of DVD emulators (think wode on the wii), they work in a pretty similar manner to the dvd flashing above in that you install them alongside the DVD and get to plug a USB drive in instead of using dual layer discs and a custom burner. Features all the same limitations as regular DVD hacking.
2) Rebooter installation. These come at the cost of live unless you are willing to go down the dual nand route for the second type which is quite tricky. They allow for things like running from USB, running from onboard hard drives, XBLA and DLC on any profile, hacked games, homebrew (it is getting there slowly but surely), system link over the internet/VPN (mind you as long as you are hacked a stock dash can host the system link game if you want), niceties like controller remapping and more.
i) if it not updated past August 11th 2009 you have the option of JTAG. This only needs some basic parts you can find in any electronics shop and maybe an older computer.
https://docs.google....mv5h_30dw33vpf4 has a basic overview, some of the names of programs have changed (fbbuild is now xeBuild) but the method is still the same.
ii) RGH aka reset glitch hack. A new hack that works on all models save some of the first and some of the latest dashes although both those are looking like they will fall in the near future. Software wise it is roughly the same as above (build a hacked dash and flash it) but instead of a couple of diodes and wires you will need a custom chip (most buy but you can build it if you are versed in basic electronics).
http://team-xecuter....ead.php?t=74857 has an install for an original style 360.
Edit- and to note below. Since time of posting (and technically shortly before it but hey first thing in the morning) those ones that did not fall to RGH have since fallen as predicted and got supported in the standard build software. You might need "RGH2.0" though and as mentioned once you have the key you should be good to update and hack from new dashes if you do it properly (although unless you want dual NAND for live I am not sure why you would) but as you would not have had it yet that did not seem that relevant.