The technique a waver employs when waving at the wavee is actually a very telling action that can determine, to the observant eye, the relationship between the two.
1. The “fingers outstretched, moving from side-to-side heartily” wave.
This implies the waver is genuinely happy to see the subject of their wave; usually accompanied by a sincere smile, with teeth.
2. The “moving fingers around in a scraggly fashion” wave.
Do not trust them. Avoid these people at all costs.
3. The “fingers prostrate themselves forwards and backwards while the palm stays absolutely still with the thumb (possibly the pinky in another variation) sticking out awkwardly to the side” wave.
Usually accompanied by a discomforted “hey”.
4. The “hand perfectly rigid, raised to shoulder level, unmoving” wave.
Usually accompanied by a confused and/or bewildered facial expression. Hostile vibes may flow freely.
5. The “timidly moves quickly, side-to-side, within a quarter inch space” wave.
This is usually paired with a creepy, no-teeth showing smile and implies the waver would rather be anywhere else except running into you.
6. The princess “hand in a cupped shape, moving stiffly from side to side” wave.
Unless this person is actually Kate Middleton, immediately walk in the opposite direction. This person is suffering from acute princess syndrome and possibly has the mentality of a seven-year-old.
7. The “double handed getting attention in a vigorous fashion” wave.
Usually seen in a huge crowd of people, which makes it easier to avoid, although sometimes the best route is to acknowledge said person to ease the secondhand embarrassment. Also seen in stressed out mothers with 5+ kids.
8. The “unbending hand moving in a one solid-motion rainbow shape” wave.
This somewhat intimate wave implies a casual friendship. Usually employed when friends run into each other unexpectedly and there’s no escape because you’ve already spotted each other. You probably want to get out of talking to them as quickly as possible. 
