Want a tip from someone that was a 158 pound beginner just a couple of years ago (currently 189)? This was some of the best advice I got on the subject and it worked for me--first of all, keep it simple.
--eat a lot of quality calories.
--if you are eating enough, your gains should be steady, but not necessarily linear (won't always be 0.5-1.0 pound gain per week, but you will steadily gain)
--do not worry about your abs
--if, after a few weeks, you stop gaining lean body mass (or you never started), then one of three things is wrong--(1) you aren't eating enough, (2) you aren't working out hard enough, or (3) you aren't resting enough.