Temp matters, someone posted that. For example, if you go green, don’t use the same temp water as black, it’ll be bitter as hell. Steep time is generally 2-5min. Dunk, don’t squeeze.

Tea additions are wide and varied. You’ll have to experiment. Sweet or no sweet. Milk or cream or black.

After that it could be anything added. Ginger. Vanilla. Mint. ???

And then there’s brewed iced tea. Brewed sweet iced tea.

Start with what you have and see if you like tea enough to spend money on more options.

How long you steep and what temperature depends on the type of tea you're brewing.

Generally the darker the tea the hotter and longer you brew for. What type of tea are you using?

And agitation isn't necessary; just do not squeeze the teabag into your drink, it will make it bitter.

Presuming you are using just standard black tea, tea bags this method is sure fire, https://youtu.be/Y-kx8JEDgnE?si=VRB4oINE3wi-6pec Not all tea bags are born equal though, so worth trying a few to find your brew. Milk or not, sweetening or not is at your own discretion really, though some teas benefit from additions, some not. Enjoy your tea journey.

I use this as a guide but I generally brew my tea a bit cooler to avoid bitterness.
https://yunnansourcing.us/pages/brewing-guide-for-green-black-oolong-and-pu-erh-teas

Green/White Tea:
Water temperature should be close to 85C Use 5-6 grams of green/white tea per 100ml of volume. Brief 10 second wash... then 10s, 15s, 20s, 30s, 45s, and then maybe a minute each time until it's brewed out. I prefer to gradually coax out the subtle flavors.

Black Tea:
Water temperature should be close to 90C Use 5-6 grams of black tea per 100ml of volume. Brief 10 second wash... then 10s, 15s, 20s, 30s, 45s, and then maybe a minute each time until it's brewed out. I prefer to gradually coax out the subtle flavors.

Oolong Tea:
Water temperature should be close to 95C (or higher). Use 4-5 grams of oolong tea per 100ml of volume. Brief 10 second wash... then 10s, 15s, 20s, 30s, 45s, and then maybe a minute each time until it's brewed out. I prefer to gradually coax out the subtle flavors.

Pu-erh Tea:
Pu-erh tea brewing is not so different from oolong teas. You want the water as hot as possible when you pour it into the pot. If you are going to use yixing, I would dedicate one pot for ripe pu-erh and another for raw. Up to you.

For bagged black tea, I use a kettle to boil water, pour it over the bag in a 15 oz mug, and steep for three minutes. If you don't have a kettle, a microwave works fine (contrary to what snobs say), but be aware that it will be hotter than you'd get from a kettle because it also heats the mug. If the tea is bitter, cut the heat and steep time. If it's not strong enough, adding more tea leaves is ideal, but adding heat or steep time can also help.

Edit: I don't agitate tea as it is steeping but I imagine it would have a similar effect to increasing steep time.

Try cold-brewing a bag or three. Easily bypasses any risk of overcooking and the attendant overextraction.