Technique

Technique is everything in weightlifting. The best lifters in the world have the best technique. Strength is important, but getting stronger on its own will not make your PBs increase. To this end, time spent practising perfect technique at weights below your max is far more likely to improve your maxes, than chasing PBs and missing more often than you make. No-one cares how much you can miss. If you haven't been weightlifting for long (or even if you have), make it your goal to never miss a lift in a session, and pick your weights accordingly. The greatest progress I have made in the last year and a bit was when I did sets of 2-5 at 75-90% for a few weeks, then attempted big singles again.