Depends on tea, mood, and if I´m alone or have guests. When I´m alone I mostly use a small, old silver pot for all kinds of black/red teas. Oolongs frequently end up in a gaiwan or one of my Yixing pots, same with Pu-Erhs. No balls/filters/screens here. When I have friends around and I´m in the right mood to produce a decent mess I usually use an ugly big horkin´ mug with a strainer. For larger parties clay or stoneware pots with cotton filters or a huge thermos with mesh strainer. I´m stuck in Eastfrisia/Germania and stopped doing Gong Fu for local friends, since they refused to drink my oolongs without rock sugar and cream. Preparing tea in the traditional local style would involve some Eastfrisean blend, heavy on strong, broken Assam, a ~1 qt metal pot, a "stoevchen" to keep it warm, a set of tiny cups and spoons - not to stir - an absolute nono - but to give signals to the host - all rounded up with truckloads of rock sugar and preferably freshly skimmed cream.
Karsten