Actually juice defender does a very good job for the battery life mainly on stand-by. If you are unsure of the settings i suggest using the ,,balanced,, option. But here are some of my tips (i use a lot of 3g internet on my phone, so the settings are a little more internet-permissive )
About tab: I selected here turn data network on screen wake-up ( i use the friends stream network, mainly for twitter updates and i like to have a 3g connection rigt after i wake-up the screen (default is turn on 3g when you unlock)
Control tab: I didn.t change here anything, the default settings are good
Schedule : I choose some peak times here ( from 12 - 16 weekdays) when the 3g stays always on, even if i turn off the phone - i recive alot of emails during this time (also i set up mail peak times during this interval to 1h update)
This is what i changed on my device. It may not suit you or any other user, but as i said, personally i noticed a good change in battery life in standby (this is what Juice Defender actually does by turning off data connection when not needed, simple but effective)