Some of the more commonly used abbreviations! 

AW - Attention Whore

BM - Bridesmaid (or can be Best Man, depending on context)

BOD - Bride Of the Day

BP - Bridal Party

BTW - By The Way

DD - Dirty Delete (don't do this)

DH - Darling Husband

DOC - Day Of Coordinator

IRL - In Real Life

FI - Fiance

FMIL - Future Mother In Law

FFIL - Future Father In Law

F/U - Follow Up

FWIW - For What It's Worth

GL - Good Luck

GM - Groomsmen

GTG - Get Together

IMO - In My Opinion

HTH - Hope That Helps

MOB - Mother Of the Bride

MOH - Maid of Honor

MUD - Made Up Drama

NFT - No Further Text

NMS - Not My Style

NWR - Not Wedding Related

OBG - Oldie But Goodie

PIB - Picture in Bio

PIP - Picture in Post

PSA - Public Service Announcement

STD - Save The Date (not what you were thinking?)

TIA - Thanks In Advance

WTF - What The F**k

WR - Wedding Related

XP - Cross Post

YGM - You've Got Mail