Which is correct?
Just thinking of you make / makes me smile.
Gerunds can be replaced with "it" (third person singular), so the answer is "makes":
- Just thinking of you makes me smile.
- It makes me smile.
Gerunds? Can you give me more examples?
Any verb in "-ing" acting as a subject or as an object is a gerund. Gerunds designate the action or activity of doing what the verb describes. "thinking" is "the action (singular) of thinking," "cooking" is "the action (singular) of cooking," "sleeping" is "the action (singular) of sleeping," and so on.
When you have two or more gerunds, they may form a compound subject, in which case a plural verb will be used:
- Swimming and diving are water sports.