A couple notes:
1. I prefer to play on 32 player servers for the map ctf_2fort. It provides more action and prevents a lot of the quick wins from occurring. On the other maps, I prefer to stick to 24 player servers. ctf_2fort is the only map that I feel comfortably holds 32 players.
2. Instant-spawn sure beats waiting twenty seconds between deaths, but it sort of defeats the purpose of capture-the-point maps.
3. I try to mix up the classes I play. I usually run as a medic for a few minutes to start a match and get a feel for where people are playing. I then focus on playing an engineer offensively, which can really piss people off, while mixing in a few rounds as the other classes.