for me, one of the easiest ways to tell isby your landscape. for instance, i dont know where you are, but i am in medford. silver maples only grow in the moist areas. flood plains, semi perched water tables, and lower ground close to water in any respects. red maples like full sunlight and sugar maples usually tend to start out under the canopy. it helps to know weather or not the property was logged, but red maples tend to be in high numbers in disturbed areas. they like to grow with aspen. sugar maples are all over, but they prefer very healthy sites. when they start growing, they are in close to full shade alot of times. does that help at all?
It doesnt matter what you tap, they all have sugar. mix the sap together if you want, theres just more water in the sap from silver and sugar. not a huge deal. careful with the silver maples though. this year, it is so late, they are going to start setting bud soon, and if they do, your syrup will taste funny. as silvers get larger there bark is long flaky sheets, whereas the other maples have hard dense bark.
the maples turn reddish and orangish in fall. real bright colors. the silver tend to turn more of a yellow, and the leaves are really thin, with deep cuts. honestly, if i were you i would start this summer by marking all the maples with the leaves on them.
100 taps on gravity
50 taps on buckets
2x4 flat pan
3 - 275 gallon tanks