Doing lifts is a vital component to CrossFit and getting stronger.  Without them, you limit your chances of getting better at workouts and increasing your weights.  CrossFit uses shoulders in almost every exercise, so they are essential to train. 
After every workout, whether it be a WOD, one rep max or a lift, you should always feel tired, exhausted or worn-out by the end of the lift.  If you are doing a 3 x 3 shoulder press, like today’s lift, then you should warm-up with 3-5 sets before you even get into the actual lift.  Your first set of shoulder presses should be at a weight where you are working hard to get the weight up, not just pushing it to get the first set out of the weight.
I picked up a methodology from Louie Simmons at Westside Barbell in Ohio a little while ago and it has done wonders for me and some other CrossFitters I know.  He talks about how you should always be training for a Personal Record (PR).  Meaning, that everyday you walk into the gym, you should be in shape to set a record for yourself, or at least get close to it.  By doing that, he says you will never be set back in your lifting or WOD’s.  Take it from this guy, he has world champion weightlifting teams year after year and follows portions of CrossFit with his lifters.   He knows what he’s talking about.  “Train at 90%,” he says, that way you are always lifting heavy and always ready to put up numbers. 
Now, this is great advice, but we must modify just a little for CrossFit.  We don’t want to use 90% of our max every time, but need to increase the weight and make attempts that push our limits.  How else are we to get better at lifting or at WOD’s? 
 Lift:
3 x 3 Shoulder Press
WOD:
100 Squats
80 Push-ups
60 Box Jumps (24″/20″)
40 Burpees
20 HSPU
Rest 1 Min
50 Pull-ups