Here are some of the common crochet abbreviations:

approx - approximately

beg - begin(ning)

bl - back loops

bpdc - back post dc

CC - contrast colour

ch(s) - chain(s)

dc - double crochet

dec - decrease

dtr - double triple crochet

fl(s) - front loop(s)

fpdc - front post dc

hdc - half double crochet

hk - hook

inc - increase

lp(s) - loop(s)

MC - main colour

rem - remaining

rep - repeat

rnd(s) - round(s)

RS - right side

sc - single crochet

sk - skip

sl st - slip stitch

st(s) - stitch(es)

tog - together

trc - triple crochet

trtr - triple triple crochet

WS - wrong side

yo - yarn over