Galco makes a nice gun belt. My next belt will be from Bullhidebelts.com. I have never had one but I have been looking and they look like a superb belt to me.
I try to "pin" my holster between belt loops so that it can not slide much. Depending on what I'm wearing some are easier to keep from moving.
Dress pants I have a tailor do the belt loops so that my holster sits between 2 that are reinforced so that they don't tear off if my gun gets on something. Could do this with jeans as well but jeans typically have better belt loops then dress pants.
Honestly if you are going to carry concealed as a lifestyle an not a hobby I suggest finding a good tailor. He/she will soon become your best friend. Ill buy a pile of clothes and take them to the tailor and get a load done for 50-100 bucks. It may seem like kind of a lot to pay extra on your clothes but unless you have a wife who is a super seamstress or are one yourself its more then worth it.