If you've decided you want to make better coffee, here are my tips for the changes that will yield the biggest results. These aren't comprehensive, just some quick tips for quickly making better coffee.

1. Don't use instant, use proper Arabica grounds.
2. Espresso is the best, then French press, then percolator. A Moka Express or Brikka are quick ways to get into espresso.
3. Use hot milk. This makes a big difference in taste, 30-40s in the microwave should do it. A French Press can be used with hot milk to make decent froth for cappuccino too.
4. Grind your own beans. A grinder is cheap, and freshly grinding your own beans just before you make a cup makes a subtle increase in flavour. Remember to store your beans in an airtight container in a cool dry place (not the fridge).