Mower wont start due to oil runnig out @ last mow.

justin, first off, all internal combustion engines have common things they need to function. Oxygen, fuel and a spark. Of course you are due for another oil and filter change. Close the drain plug. Check your spark. Check the timing, make sure your flywheel is properly aligned on the crankshaft. If you have spark, check for fuel. Check your carburetor, fuel lines and tank. Make sure they are all in working condition. Check your float and needle valve inside your carb fuel bowl. Make sure that you have plenty of air reaching your carburetor for a proper fuel/air mixture. Now you could get more specific answers if you can give us a motor model number and be more specific about what mower you have. As with anything, take your time and do one thing after the next. Do not get lost in the troubleshooting and start tearing things apart, be systematic. Hope this helps to get you started.