Pick up a handheld transceiver, and use it to get ATIS info before starting the engine. If you need to contact a fuel truck after landing for a top-off, use the handheld. I figure if I'm saving .1 on the Hobbes on flights, where I rent from that's $18 each time. Handheld pays for itself quickly, and you've got a backup in case your electrical system fails.
If you're paying by wet, fuel included Hobbes Hour (constant increments while engine running or however actuated), it makes sense to cruise fast. No sense in trying to save fuel unless you need the range. If you're paying by Tach Hour, that's different. That's RPM-dependent, so you'll run up less tach hours at slower cruise and while on the ground waiting for clearance or release.
Speaking of waiting on the ground, if you're at a field with a fair bit of IFR traffic/bizjets, consider requesting an intersection takeoff if there's a bizjet at the full length hold short. I've gotten stuck behind jets several times that are waiting for release or are getting new routing. During my PPL training, flying one of my long XC's, I waited 25 minutes (about $70 for me) for a jet in front of me to get released. My instructor later told me about using an intersection.
Also, seems obvious...organize your cockpit fully before starting the engine! Doesn't make much sense to fire the engine then start arranging sectionals, kneeboard, etc.