Step by step - an engine needs 3 things to start and run: air, fuel, spark. Test for presence of each one until you figure out what's missing.
Spark: pull a spark plug wire but leave the end close to the plug or some other metal part of the engine. Try to start it, watch and listen for spark jumping. Get someone to help if you need to. No spark? Could be points, bad coil, bad plug wire (try several different ones), bad coil wire, no power getting to the coil (test for voltage present on the primary side using a meter, with ignition on). If you get spark this way but still no joy, remove a few spark plugs and look at them. If they're obviously dirty and very wet, could be too fouled to fire - give them a good cleaning with a wire brush, re-gap, re-install and try again.
Fuel: Remove air cleaner, lean over and look down the carb as you slowly open the throttle by hand. You should be able to see fuel squirting when you do. No squirt? Could be out of gas, clogged in-line fuel filter, bad fuel pump, clogged fuel line. Try pouring a thimble-full or two of fuel down the carb throat then try to start it (careful! stand back) - could be the fuel bowl is empty and the pump just needs a little "help" to get going again.
Air: try with air cleaner removed - make sure choke isn't stuck shut.
You'll get there.