Depends on the type of love spell I suppose...
A)If you perform a spell to sweeten someones feelings towards you: If they like you (romantically) already it will deepen their feelings for you thus giving them the courage to tell you those feelings, or the latter: if they don't romantically like you the most you'll get is friendship.
B)If you perform a spell to force someone to fall in love with you: They might go stalker mode on you: They might go crazy thinking about you: They might fall in love with you if they do have some feelings for you but then never leave you alone
C)There are defiantly karmic repercussions when messing with peoples emotions
D)Tread lightly around love spells
E)Try love spells that find/bring your soulmate/lover, that way your not messing with peoples emotions and well-being as much as the forced love spell
F)Keep an open mind by not targeting a specific person or the "perfect" image of what you want: keep the list of qualities to the important minimum (I don't know a single person who has the perfect "ken doll" of a guy they want)
G)Love spells that work for one person may not work for others
H) GOOD LUCK! and BLESS IT BE