ASVAB and MEPS help? What to expect?

Okay so I take the asvab In a few days. I'm still in highschool as I graduate next year. I'm so confused... Am I taking the meps the same day as asvab? Will the drug test me before, after the asvab? Can I request that I go to meps at a later date? I've also tried pot twice but that's it. What do I tell my recruiter about that? Someone please help me!!! Thanks in advance. I look foward to serving my country in the future.