I've had to do this before and if you were really into working out before (had a good base) you should have no problem getting back into it... you'll be surprised how much memory muscle has.
You should start out with a full body workout no more than 3 times a week for about a month, this of course is with light weight 3 sets of 10. You may be sore the first week back so don't overtrain, wait until you aren't sore to workout again. My first week back i could workout maybe twice because of soreness.
The second week, same concept, train up to 3 times that week full body, light weights, high reps.
By the 3rd and 4th weeks you should be able to workout 3-4 times per week full body, depending on how you feel you could start doing one body part per week by week 5 or so with 3 sets of 8, 2-3 excercises per muscle group.
I have had injuries that i have had to quit lifting for a number of months and this has always worked out for me. Just be sure not to over do it the first few workouts.