you need INT gears for lock picking (THF AF head +5, Ice Staff +10, rings +2-3 per ring, belt +1 or 2, w/e) otherwise you may end up losing more money on thief tools than needed, if the area lvl is kinda too high ( I am speaking like 15+ lvls higher) and you see a coffer at a spot that seems to be too good to be true, don't try to mess with it more than 2 times, it's most likely a simulate, there is only 1 simulate that pops in a bad spot that I can think of, the one in the mid of the leaches @ castle oztroja... some areas have more than 1 simulate, Vu'Lugannon Palace. NPC.exe will show simulate's and coffer's ID within range and MrArgus is very helpful and detecting which are which by inputting their ID's and pressing "To Mob" and type of tool also gets involved, Skeleton Key seems to work the best so far.
as for map's and coffer/chest location you can go to
http://ffxi-atlas.com/
note: if it's a coffer and not a simulate, failing too much may end up in triggering a trap, a weakened that would last for an irritating period of time.