In my experience there are at least a couple types of butt pain. :) The primary one is what you get when you first get on a bike, or after you've had a lay-off. It's just a matter of toughening up your skin and sit bones and other parts, which happens naturally after a couple weeks of riding regularly.
I deal with that one a lot these days because it's not uncommon for me to take a month off the bike (forced time off, due to adult responsibilities). When I get back on the bike each time, it takes a couple weeks before I reach the point again where I'm not squirming all over the seat the entire ride, trying to relieve the pain/chafing.
A good chamois cream helps. A good substitute is any thicker lotion that has lanolin in it.
And of course, bike shorts are mandatory. I wear mine under some baggier shorts these days, but never do any riding other than commuting short distances without bike shorts with a well-made chamois. My favorite brand are Sugoi. The liner chamois that come in most "baggy" cycling shorts are total crap. Cardboard. I have cut a few liners out so I could just wear my favorite bike shorts under them.
Without bike shorts, expect pain.
Now, that's the most common type of butt pain. The chafing and sit bones pain. Time will take care of it. What I saw happen over and over in bike shops: guy comes into the shop, buys a bike. Hasn't been on a bike in years. He rides it a few times and comes back in going "I need a bigger seat with more cushion; my butt's killing me." So instead of taking the time to let his butt get used to riding, now he has a HUGE seat with padding and springs shoved between his legs every ride... which believe it or not is actually more painful than a smaller seat, and will increase your chafing.
That guy gets his Big Seat and goes home. He will do one of two things: either put the bike in the garage and not ride anymore because the seat hurts his butt OR he'll decide to ride through it and a month later his butt has gotten used to riding and he attributes it to his Big Seat and spends the rest of his days riding an otherwise cool bike with an enormous seat on it that looks like it might fit a Harley-Davidson.
I'm not saying there aren't seats out there that just plain suck. Many of them do, particularly the ones that most bike manufacturers put on their entry- and mid-level bicycles. But don't just run out to find a seat with more padding... instead, try to find a light, low-profile seat that is actually shaped in such a way that it doesn't offend your ass-saddle interface. LOL
The other kind of butt pain is a fit issue. Speaking in general terms, you want your weight divided evenly over three contact points on the bike: your butt, your hands and your feet. If any one of those are taking too much weight, they are likely to cause you problems. If you already have problems in one area, you can adjust your cockpit so that a little less weight is on that body part. For instance, it's common for people to have carpal tunnel. Most of them who are willing to put some time and money into adjusting their bike fit will eventually find relief by shifting their weight off of the hands and onto the feet and butt.
If your butt hurts, you may try standing more often. Same for erectile dysfunction issues or numbness... stand up for 30 seconds every 10 minutes, minimum. There was a study done ten years or so ago, when every bike and fitness magazine had an article in it about cycling causing ED, that showed that most cases of cyclists having ED could be alleviated by the person making a point of NOT sitting without standing for long periods of time.
I could ramble on and on, but I need to get to bed because we're doing a 6 hour mtn bike ride tomorrow morning at 4:30 AM. Not all that stoked about it, but I'm not one to wimp out. :)
