All the above plus:
If you're taking the train, you're probably staying in the Leander/Cedar Park area. Check with Capital Metro to see if they'll have expanded service during the fest. Austin isn't known for stellar public transportation and it would be an expensive cab ride to get out there from downtown.
The Austin Chronicle is the weekly arts and music newspaper. They're on line. Also, during SXSW they usually publish a daily edition. You can read their Picks and Sleepers article to get an idea who you might want to see. Hardcopy of the newspaper is readily available at bars, restaurants, grocery and convenience stores. Do as much other homework as you can on bands to see and where the concentration of venues are. Mostly the venues are centered on downtown but that's subdivided into various areas.
There are a lot of venues that are not venues any other time of the year. Don't let this dissuade you from checking someone out. There have been amazing performances in parking lots, yards, etc. Also, some fantastic afternoon shows.
There are also a bunch of shows that are not affiliated with SXSW. Just because a band is playing doesn't mean it's a SXSW showcase. You can catch some really fine local entertainment just walking down the street and likely for free. Also, there should be some bigger outdoor shows.
If you're interested in music from other places, there will be venues that devote an entire evening to a specific part of the globe. (e.g. Scandinavian night).
It froze here last night and freezing rain is predicted this evening. The weather should improve by next week but it's been a weird year so far.
Non-music: there are a lot of good restaurants downtown. Kind of hard to go terribly wrong, depending on your taste in food. We like our Tex-Mex and barbeque here. Barton Springs pool in Zilker Park near downtown is a civic icon and nice to visit and it's just off of the hike and bike trail along Town Lake which is also nice. If you like history, the Capitol Building is actually pretty interesting in a Texan sort of way.
Pace yourself, it's easy to overdo it. Oh, and an extra pair of comfortable shoes.
