This worked for me:
1-Read manual cover to cover.
2-Sit with gps in hand and repeat step one.
3- Go outside, record a WP for your house and go for a walk.
4-Experiment with everything: track logs, trackback, entering WP's, GOTO etc. With mine I took it on my running route through a maze of streets recording a tracklog and WP's. Then I redid the route and checked it for accuracy.
5-Take it on a trailed hike.
6- Explore every function and sub-menu your unit has.
7-Never be shy to ask questions, DougPaul will help!
I learned a computer mapping program at the same time (National Geographic Topo!) and read a great little book published by the Mountaineers called "GPS Made Easy".
I would recommend to anybody just getting going to start with a simple model and rely 50-50 on map and compass and gps while out in the field. Then maybe later upgrade to a mapping and electronic compass unit.
Anecdote: when my gps was in the shop we used my friend's very basic Etrex for a bushwhack in the Sawtooth Range. We manually punched in the UTM coords for 4 or5 WP's pre-hike and turned it on from time to time to check distances and bearings to the next WP. Just this simple utilisation was a huge leap beyond straight map and compass.