There are some people who do home improvements in their home because they think that it will improve their chances of selling or mean they make more money from the house when they do sell. This is something which may or may not work, it really depends what the potential buyers are looking for.
If you are intending on staying in your home for a while, then it is best to make improvements that will benefit you. This means that if you do not get your money back, you will not feel so bad because you will have got use out of your investment yourself. So do not convert your loft to an extra bedroom because you think it will be desirable, but if you need more space in the kitchen consider doing something about that instead by extending the ground floor or rearranging the layout.
Home improvements can be very disruptive as well and so unless you can guarantee that you will benefit from them, then it is not worth the disruption. The cost can be difficult enough to manage but having to live on a partial building site can be extremely difficult, especially if you have children in the house. If you are only doing work to increase the value, it could be better to wait until just before you sell so that the work you have done is up to date and to modern tastes.
It is always a good idea to use good workmen for the job. You will need certificates for electrical works that are carried out so make sure that you use qualified people. You also want to make sure that the job is finished, good quality and on schedule so picking a good team to do the job is therefore very important.