Is there a different sign for 'meet' and 'met'?
No, ASL does not conjugate verbs for tense like English does. You use the exact same sign for 'meet' and 'met'. To show that the meeting happened in the past, you simply add a time sign like 'yesterday' or 'past' at the beginning of your sentence.
Can I use this sign for a business meeting?
No, this specific sign is used for the action of people meeting each other. If you are referring to a gathering or a business 'meeting' (the noun), there is a different sign where the hands open and close together.
Does it matter which hand moves?
In the standard sign, both hands move toward each other to meet in the middle, showing a mutual meeting. However, this is a directional verb, so you can move one hand toward the other to specify who is meeting whom (e.g., moving your dominant hand toward your stationary non-dominant hand to mean 'I meet you').