Is there gas in the tank?
1. Turn the petcock on and lean the bike over for about 5 seconds and then back up. See if gas runs out of the over flow tubes under the bike.
a. If yes go to 2
b. If no then turn the petcock off, remove the gas line (between the petcock and the carb) and then turn it back on for a second and then off again. No gas than your problem is the petcock/Tank, if there is gas then your problem is the carb.
Spark plug / Spark
2. Remove the spark plug. Using a new/clean plug place the cap back. Wear gloves for this part, place the plug against the head (have the threads touching and that is it) and rotate the motor over (use your hand on the kick starter and press medium speed)
a. If you have spark then put the plug back in and try starting the bike.
b. If you do not have spark, you need to check all the wire connections. If they all look good than you may have to take it to a shop (more than I can explain here)