Try to reproduce the conditions it would find in the wild. Most plants prefer to dry out a little between thorough waterings. Water from below - stand them in a dish of water until all the water has been taken up. Feed regularly to keep them healthy. Avoid strong heat or chilly draughts.
Many houseplants like to be outdoors in summer - check all frosts are over first.
Do not buy plants that have been standing in the cold, as they may be frostbitten. Check your plants regularly for signs of stress, pests or disease. Remove dead leaves and flowers as they occur. The key to success is simple - find out where your houseplant originates from, and try to provide those conditions as best you can. Or choose houseplants that are suited to the conditions you have in your home.