Most used:
* - repeat
dec - decrease
cont - continue
inc - increase
k - knit
k2tog - knit 2 together
p - purl
p2tog - purl 2 togehter
rep - repeat
RS - right side
sl st - slip stitch
tog - together
WS - wrong side
yo - yarn over needle
Others:
C3B - cable 3 back
C3F - cable 3 front
foll - follow
M1 - make 1 knit
M1P - make 1 purl
oen - on each needle
patt - pattern
psso - pass sl st over
p2sso - pass 2 sl st over
rem - remainder
skpo - sl 2tog, k1, psso
s2kp - sl 2tog, k1, p2sso