From left to right (all AquaChem):
1. Shock Xtra Blue - contains copper-based algecide. Any other kind is a waste of time and money. On cool cloudy weeks I put 2/3 bag once per week or when the test strip says "low" available chlorine.
2. Chlorine tablets to put in your floating dispenser. I use 2 whole tabs and add another when the previous tabs are half disolved (about 1 tab worth).
3. Test Strips. You can use the water sample method like I used to but that only gives you pH and total chlorine. The test strips give you a lot more information and they're cheap.
4. "pH Up". The rain these days is pretty acidic so it brings the pool water's pH down. This additive brings it back up.
5. Flocculent - AKA Water Clarifier. Don't over-use this or it will make things worse. I only use it after I've shocked, balanced, vacuumed and filtered the water and there are still traces of tiny particulates. I usually only get to this point if I've put off treating my pool for too long.
6. "pH Down". This is acid. Just like it says, it brings the pH down if it's too high. I wouldn't use it unless the pH is way high. I've only used it once, immediately after filling the pool for a season when tap water had it too high. Normally I'll just let the rain bring it down.
7. Nylon sweeper. I use this to stir up the bottom after adding chemicals. That way I know they're mixed well.
8. Graduated jar or measuring cup. Used to measure liquid chemicals. I just estimate with the powders, slowly shaking them out as I walk around the perimeter of the pool.
9. Stabilizer (not shown). This keeps PH and chlorine levels from fluctuating so much - translates to fewer required treatments. Follow directions on package. It takes a lot longer to dissolve than shock.