Your best bet with a State Park, from my experience is to keep as low a profile as possible, you gotta go Hobo Ninja with that shit!.
#1. Keep your campfire very small and don't keep it burning all day and night. The flicker of a small fire is harder to see at night, especially if you dug a pit for it. Use wood that won't give off a lot of thick smoke which will cause your spot to be revealed by day when someone either sees or smells the smoke... NEVER use Pine wood, burn leaves or burn trash.
#2. Keep the noise down, music, yelling, general camp noise, etc. You would be surprised how often noise will travel. When camping with other people in such a location I will sometimes do a security check which consists of concealing myself along the closest road or path, and just listen, smell and look for the next half hour. If you can't hear, smell or see any movement from your camp... you're completely hidden.
#3. When selecting a site stick to the borders or fringe area of a Park. People often seem to have the urge to go deep into a forest to get away, but in this case, unless the Park is massive, you are more likely to get caught. The Rangers or Park police will patrol the main roads going into the heart of a Park, that's also were "nosey yuppies with cell phones" will be hiking. Also the border and fringes of a Park are a much larger and spread out and nearly forgotten area to patrol, and the lines between Park land and private land get blurry... blurry can good. You may still encounter hunters on occasion, both in and out of season. But they are usually pretty chill and respect here is a two way street. Keep your camp clean and remember to tell the ones who are hunting out of season that "hey I never saw you."
Another bonus is that sometimes you may find an abandoned farm or house in the border area. The border and fringes often provide a longer stay. The smell and smoke of your campfire will also raise less alarm in this area.
#4. Avoid State Parks with established camp grounds. These have a stronger presence of Rangers/Park Police who patrol more often. You won't have the maybe get out of a ticket excuse of "hey, there was no place to camp".
#5. If you are gonna go deep into a Park to camp move your spot every other day or at least twice a week. If you stay put, sooner or later some unwanted visitor will stumble onto your camp.
#6 Never take the exact same way into your camp repeatedly, if you do you will wear a path leading right to you. So many people make this mistake.
