[HTC Incredible S] key2gb:
For Incredible S there is only one way to do this, and that's with the revolutionary tool, found here: http://revolutionary.io/

Download that tool and type in the necessary info you need to get the beta key

Make sure that during this, your phone is connected to your Windows PC via USB, and that USB debugging is checked ON (Settings > Applications > Development). Also make sure that Fast Boot is turned OFF(Settings > Power > Fastboot).

Once you have the beta key, open the zip file that downloaded and open the .exe file, it will bring up a command prompt (btw, you CANNOT have HTC Sync on your computer. Uninstall it if you do, or this won't work). In the command prompt, type in your beta key (case sensitive) and press enter. The revolutionary tool will now attempt to convert your phone to S-OFF. Congratulations, you have rooted your Incredible S! The developers that made that tool got your back, and the tool automatically creates a backup of your system as it is at that moment. That means from that from the moment your phone is rooted and on, if you ever mess anything up by flashing a ROM that isn't compatible with your OS or do anything to mess your phone up, you can reboot the backup file (saved on your SD card so it will never go anywhere) and you are back to normal the way you started, so no worries. You are free to experiment. You'll also notice you have a new recovery boot screen - that's ClockworkMod Recovery and it is installed automatically with the revolutionary tool. From now on whenever you want to flash a new ROM or make a backup without ROM Manager - you can "Boot to recovery" and it will bring you to that blue and black screen. From there you can create a backup, or mount your USB to your PC and move files onto the SD card (necessary for flashing new ROMs).

Now you need to ask yourself why you rooted your phone. If you're like me, you'll want a custom ROM and a new interface. Or maybe you just want a few apps that require root access. Either way - here are two logical next steps:

1) Download Titanium Backup. Shell out the money for the paid version if you can, it's worth it. If not, you can grab the free version. This app is perfect for backing up your apps AS THEY ARE. Do you have 3 stars on all Angry Birds levels and are afraid that switching to a new ROM will delete all your data? Fear no more. Download and install Titanium, go to the middle tab called "Backup/Restore", press Menu and go to "Batch" This automatically batches together your User Apps that you want to backup. BTW, after your phone is rooted, many apps will ask you permission to grant it root access. Always allow and always 'remember'.

Once your user apps are backed up, you can install a new ROM. Once your new ROM is installed, go back to the market and download Titanium again (yes, again, since after installing a new ROM, your apps are gone). Luckily, your apps are synced to your gmail account, so when you install Titanium back to your phone, it has all your information backed up, even though you technically uninstalled the app . Titanium is a miracle worker.

2) Download ROM Manager from the app store. Search the forums if you are interested in learning about ROMs. If you want to get straight into the action with a program that does the work for you. Go to ROM Manager > Download ROM, and download one of the choices it gives you, but DO NOT download Cyanogen Nightly unless you really know what you're doing. However, CyanogenMod 7.1.0 RC-1 is a perfect choice, and you'll find it's actually one of the most used ROMs. Download that one, and you'll also be prompted to download Google Apps along with it, which you should definitely do. It will ask you to clear your cache and davlik cache, which you MUST DO. Remember you already have a backup, so no need to make another one at this point. Check to clear caches, then it will reboot you straight into the process. Congratulations, you've installed your first custom ROM

Once Cyanogen is installed, go to the market and download Titanium, and re-install your backed-up apps by going to the middle tab and pressing menu > Batch, and scrolling down to "Restore". Click the "Run" button nect to "Restore missing apps with Data"

Now if you paid for Titanium, your work is done. If you didn't, you have to install one-by-one (basically just press Install a bunch of times instead of it being automated - it's not as laborious as it seems). Now you are running a custom ROM with all your old apps and you are now free to explore the world of rooted apps and system management.

2a - you said you wanted Sense 3.0, so choose a ROM that comes with that (I think Android Revolution HD does? not sure but search in the Sensation S development forum and you'll see all the ROMs available and what they come with). ROM Manager won't do the work for you on this though - you have to download the files and put them on your SD card (the same way you do it with the Revolutionary tool), then flash the ROM and corresponding kernel one by one (the link for the corresponding kernel will usually be given to you along with the ROM so it's just a matter of downloading it). Once the new ROM is flashed you can create a backup of it with ROM Manager (or you can do it from the Clockwork boot screen)

By the way, this question gets asked many many times here, so definitely do a search - the information is all here.