A Good Pot of Tea

Actually, I’m asking: How do you make a good pot of tea? Mine always seems bitter and I’ve been using a quasi-scientific method of elimination to determine the cause, but no luck. I try steeping in fresh boiled water for two, three, five minutes, or just leave the dang tea bag in there. I usually use two cups of water per one-cup bag, but have experimented with one cup per bag, 4cups/bag, etc. I try pre-heating the pot with boiling water; pre-heating the glass or mug with boiling water. With sugar or honey and without.
I have a nice tea pot. The Moms picked it up in Japan 30 years ago and recently passed it down to me. It’s off-white and porcelain-looking, your typical round tea pot. Wicker handle. Small screen inside over the entrance to the spout. Cute little round lid with breathing hole. Don’t generally do more than rinse it out, but cleaned it briskly once or twice with scrubbing and dishsoap.
The actual tea I currently use is Tetley, Orange Pekoe, box of 170, round, one-cup bags. Had similar Red Rose brand before, same result. Suggestions?