Garmin user manual - eTrex 20 and 30 - Online manual here
We have many more tips and training videos to get you going with your Garmin Handheld GPS device and Garmin's Basecamp planning software on our Online Training Resource - More info here
You can also when logged in view videos for the newer etrex22x & 32x units which you will still find useful for the older model as very similar and there are a lot more training videos for the newer version.
Buy and learn from the experts - GPS Training