Yeast is the soul of your beer.
The way to look after your yeast is to ferment at the correct temperature. This includes having the wort at the correct starting temperature.
If you are using kits from the supermarket, the kit will have an ale yeast (even if the tin is marked lager.)
Ferment ales at 18-22. Preferably at 18.
If you buy your gear at a homebrew shop and you buy a lager or pilsner, ask the seller is it a true lager yeast. If it is a true lager yeast, brew at around 10-12 degrees.
If you decide to use a different yeast, then follow the maker's suggested temperature range. Many specialty yeasts need good control to get the wanted flavour profile.
When pitching your yeast, make sure the wort is at the correct temperature. If you pitch at 30, the yeast will take off like a rocket, finish in two days, which is just when you will have managed to drag the fermenter temp back to 20.
Sanitise up some clean plastic containers, takeaway containers work well, fill them with clean water and freeze them with lids on. These iceblocks make it easy to get your wort down to the correct temperature. Defost the iceblock out of the container and drop it in the wort.
Kit twang usually comes from using stale ingredients. But many other factors can also give bad flavours. Infections, hot ferment temperatures and stale ingredients are the main culprits giving poor results.
Don't rush your brew, keep it clean and cool, leave it in primary for 12 days before thinking of bottling, check using a hydrometer that it is stable over a few days, buy your gear from a good homebrew shop, join a club and keep reading AHB.