Taking care of your hair extensions will not give you a lot of extra work. Here are just a few tips that will help to keep your extensions and your hair in a better condition.
First of all follow the instructions given to you by your stylist.

Washing:

Keep your hair clean. Hair tangles when dirt and sweat build up, wash your hair after exercise, swimming etc. Brush your hair and remove all tangles before washing it. Wash your hair going in a downward motion. Use a good quality shampoo, your stylist can advise you what product is best for your hair. When lots of water is added at once to very dry hair, hair can swell up and tangle. Gradually wet the hair and brush gently before you completely wash it. This is more common with less expensive extension hair.

Styling:

When brushing use a soft bristle brush, start at the ends of your hair and gently work your way up. Always brush in a downward motion. Do not brush harshly. Brush your hair 2 or 3 times a day. Heat is your one of your hair's biggest enemy, the more you use it, the shorter your hair extensions will last. Be careful with the use of blowdryers and curling irons. It is best to let your hair dry naturally.

Exercise: 

Wear a cap when swimming or keep your hair out of the water. Chlorine and salt water can cause the hair to tangle and mat up. It is recommended to wear your hair up or in a ponytail when you swim or exercise

Sleeping:

Never sleep on wet hair, make sure your hair is completely dry before you go to bed. It is also recommended to wrap your hair together or gently tie it up to prevent tangling.