Hi there, i'm new to lifting weights and in need of some help with what muscles to work in each session i have a sort of plan so will lay out what i know here :-

-Three x Two hour sessions a week (Mon,Wed,Fri)
-I want to be more in shape for Mountain biking - Squash & Inline skating.
-Going to do one week session with 12 reps and next week session with 6 reps (i am thinking this as i don't want to build big muscles just more defined and powerful - and iv'e read its good to mix up a bit so your muscles don't get used to one thing all the time)

I want to know basically how to split up the muscles between each session and is there any muscles that are better to train at the same time or to not train at the same time?

Thanks for your time and all responses are very welcome