New to this, how often should i train.

 
As mentioned in some other posts ive just started training. I think ive got my diet sorted, im just not sure on my training.
 
How important is it to have a set routine? I have loads of enthusiasm and alot of spare time, so ive found myself in the gym alot the last couple of weeks. About 5 days out of seven. Im unsure how much rest i need in between workouts etc. Ive been reading up loads on it but theirs so much info it gets confusing.
 
As i said, i dont have a set routine, i just focus on one muscle group each time i go. Most of my mates train so i generaly just train what they are training as long as im not still sore. This week for example it has went somthing like
 
Monday - shoulders
Tuesday - chest
wedensday - off
thursday - arms
friday - chest
 
I plan on doing my legs tommorow as they have been neglected.
 
Im still a total newbie so it will be a major ball ache going through my routines in detail because i dont know the names of some of the exercizes i do :P. At the minute im learning somthing new from someone everytime i go. Is their a general rule for how long i have to wait before training a muscle group after the last session?  At the minute im loving it, i feel fresh and each time i do chest im upping my bench a little.... i can comfortably bench 40kg for 10 reps and a month ago i couldnt lift 20! So im getting stronger.... i just have a feeling these newbie gains wont last long.

If new to training do a full body routine (a beginner one)
 
Monday
Squat
Bench Press
Bent-Over Rows

Wednesday
Deadlift
Overhead Press
Chin Ups

Friday
Squat
Dips
Power Cleans
 
All 5x5

Preferably trainings not more than 3 times a weeks, every training should not more than 1H. The routine give by "The Truth" is a good training plan for beginners, make sure you give some time time for yr muscle to rest and recover so you can maintain your exercise routine without getting muscle strains that will make a reverse effect from wat you r doing for a whole lot time.   

thanks for the reply mate. The full body routine is obviously benificial for a beginner but why? If i was to take somthing like this up id be doing it on my own as my mates dont train this way. Slight problem as im not confident enough or motivated to push myself etc when on my own. Obviuously it makes the gym much more enjoyable when i have a partner to work with and match their routine. Am i wasting my time doing this?