Newb here... General Advice

Be alert for battery problems. Those batteries are getting very old indeed and may need to be replaced. The XT/350D has two batteries: the main rechargeable battery, and a "button" battery for the date/time clock. If that button battery starts running down, the camera can start doing strange things. Easy fix, if you know what to look for.

As far as memory cards go, the XT/350D can't make use of memory cards over 8GB. You could put, say, a 16GB card in there, but you'll have to format the card in the camera, and it'll only format 8GB. Also, it doesn't have much use for anything faster than 80x or so. The old SanDisk Ultras were a good match speed-wise. But cards are so cheap now, if you buy more speed and capacity than the camera can make use of, it's no big deal.

Speaking of memory cards: the "shots available" counter can't go above 999. So even if you have room for 20,000 shots, it'll say 999 until what's left finally drops below that. That wasn't an issue back in the days of 128MB cards.

Be careful what you have on your hands when you handle the camera. The rubbery parts can melt or disintegrate in the presence of DEET bug repellent, and I've heard similar things about some hand lotions. But given the age of the camera, they're probably already long gone due to simple friction.

The camera will rattle if you shake it. Maybe you shouldn't shake it. There's an orientation sensor (portrait/landscape) that rattles, and the arms on the pop-up flash can rattle when the flash is folded down. Do not freak out over rattles.

Connecting the camera to a computer using the USB cable can sometimes produce unexpected results, especially if you're still running Windows XP. A good CF card reader is usually a better way to transfer your photos.

You might want to download the latest version of Digital Photo Professional (DPP), Canon's official Raw-file converter. If I recall correctly, Canon finally made the latest version of DPP work with the old XT/350D. If you don't have an older version installed, there's some trick to downloading the new version but I don't remember what it is. You'll have to ask here on the forum (unless someone responds to this.)