To replace your cables often... even if they feel good. Here is my rear derailleur cable which was planning to convert my roadie to a single speed when I least expected it!
Brake cables are next as they are a little crustified and are not as smooth as I'd like them when I'm cm's away from other wheels at high speeds.
Aplogies to Jaywoo.... next time I'll post this reminder a few weeks before you snap cables out on the road! :)