Last summer my friend and I drove from PA to Mt.hood it was one of the best experiences I have had in my life no doubt. You can camp at Lake Trillium for up to 2 weeks at the same camp site after that you have to move to another site. This is the same area as the airstrip minus all the wreckless parties.
DO's
Take showers at Mt. Hood RV Park
Bring a power converter the come in so handy
http://www.walmart.com/ip/15406269?adid=22222222227009372168&wmlspartner=wlpa&wl0=&wl1=g&wl2=&wl3=13999191310&wl4=&wl5=pla
Bring a cooler and mini charcoal for post skiing fun
Hood River Skatepark
Punchbowl falls (cliff jumping)
Portland
Cobra Dogs/Taco Shoppe
Alpine slide @ ski bowl
Bring a tarp to put over your tent in case of rain
DON'Ts
Get caught poaching camps
Get lost in mt. hoods back country your probs going to have to hike out
Buy gas in Govy its way cheaper in sandy
Get pulled over by the cops i got a $400 speeding ticket on mt hood highway
hope this helps