The engines starts backwards because it's overprimed, or a bit flooded. To avoid it happening adjust your priming procedure so that you aren't getting so much fuel in the cylinder.

Here's what I do:
- Without the glow starter on the engine open the throttle wide open.
- put your finger over the air intake in the carb, or over the exhaust outlet on the muffler if you have a cowled engine.
- Flip the engine counterclockwise until you see fuel pull up and start to enter into the carb.
- Flip it over a few more time to move the fuel into the cylinder.
- close the throttle to idle and put the glow driver on the glow plug
- start the engine.

If it still runs backwards reduce the number of turns you flip the engine after fuel enters into the carb. If the engine doesn't fire when you flip it increase the number of times you flip it

Hope this helps

Ken