First of all if you're a girl, make sure you trust your male friend. (Unless genders are not an issue here). Secondly, like others in the comments said, pace yourself, keep hydrated, stick to low alcohol drinks like beer, don't turn it into a challenge or a show-off of how much you can drink or smoke. Thirdly avoid driving. And last but not least, have fun and hope you don't puke a lot. Cheers!