Be kind to the seams. Seams last longer with less strain. When changing, always grab from the knee pad, not above. Pull up from below a seam instead of right on top of it.
Mind the smoothskin panels. Take special care to avoid stress where smoothskin and jersey panels meet, and keep your suit away from sharp objects such as branches, nails, etc. Use the palm of your hand, not your fingers, to adjust the smoothskin.
If you're between sizes, choose the one that feels comfortably snug rather than painfully tight. The neoprene will mold to your body with wear, and suits can shrink slightly with age.