With regards to safety - it would be best not to touch the oxy - it is hands down one of the most addictive substances available to man.
That being said, I remember being young, and doing what I wanted - regardless of the warnings.
If you do decide to take the pill, please take the following advice:
1. DO NOT SNORT IT! Because it has 325 mg of tylenol, it will burn terribly, and while higher plasma levels can be achieved via snorting, there is much greater bio-availability from swallowing the pill. If the pill contains tylenol, or is under 30mg of oxycodone, I always suggest SWALLOWING the pill to get a BETTER HIGH.
2. Xanax will potentiate any opiate, but I DO NOT RECOMMEND MIXING THE TWO. Mixing xanax and oxycodone is what we resort to when were deep in our addictions, struggling to get high off our usual dosage. For your first time, simply swallow the percocet with some water (juice, whatever), and give it about an hour.
3. Smoking weed is relatively harmless, and will help potentiate the high. If you decide to take the pill, wait the half hour - hour, and once you begin feeling the effects, feel free to roll a join / pack a bowl. It will definitely intensify the effects slightly, without the level of danger potential that would come from mixing xanax and oxycodone.
4. If it is your first time, and you are looking to get "REALLY HIGH" 5 mg may be a little underwhelming, although if you are fairly small/light-weight it may suffice. I would recommend 10/mg a safe first-time recreational dose, but DO NOT EXCEED 15mg your first time. I would honestly not even exceed 10mg your first time. Most would probably say just stick to the 5mg, as we never know how our bodies will react to the drug. Even the most seasoned heroin addict will start with a very small sample from a new batch, before snorting/shooting/smoking their usual dose.
5. Do know that oxycodone is 100% the same family as heroin. You are not considering using a benign drug - it is highly addicting, can ruin your relationships, and potentially kill you.
Please be safe. Do not mix with any other pharmaceuticals. Do not exceed 10mg your first time. And DO NOT SNORT IT!
Take care.