95% of a good paint job is in the surface preparation. If the surface is not clean, dry, properly puttied and caulked the final paint job will be lacking.

Remedy: Scrape loose paint, wash down the surface with tri sodium phosphate (TSP) or pressure wash ( outside only). Let the surface dry then lightly scrape and sand the remaining areas of loose paint and then prime all bare wood with a good quality wood primer. After priming, caulk and putty all cracks, holes and nicks. Wear a dust mask when sanding and scraping old paint as it may contain lead. Now you can paint the entire surface with a final top coat of paint . Be sure to apply two coats of paint wherever you primed that there was bare wood.
 

III Do It Yourself Vs. Contractors
For some folks it pays to hire a contractor and let her/him just do the work. For others it is better to do the work themselves or hire a craftsperson and participate in the work being done. In either case an informed and knowledgeable homeowner gets the best quality work at the lowest possible price.

The Owner Builder

In most states the home owner can legally do any repairs on their home as long as the permits are obtained and the work is done according to local building codes. They can also hire people to help them in areas that need more expertise or extra hands. The advantage of this approach is that you have more control over the work being done and can usually get it done at a lower cost. It is also a valuable and enriching experience to participate in the work being preformed as much as possible. Ask as many questions as you feel necessary to feel confident that the work is being done to your expectations. One can get a good skilled craftsperson by checking their references and looking at previous work or photos thereof. Some stores give lectures on basic plumbing, electrical, tile and carpentry work. These lectures are usually free and taught by  competent and knowledgable staff.

The Contractor

Sometimes a Contractor is the best choice, especially for those who don't have the time or desire to organize, direct or participate in the construction/repair work. It is however important to have some rudimentary knowledge of what is being done and have checked with the clients that the contractor has worked for in the recent past and seen previous work either first hand or photographs thereof. Any good contractor who takes pride in his/her craft will be happy to provide some examples of their work. It is also good to ask their previous clients if the contractor was considerate and professional in their contractor/client relationship.
    Being a licensed contractor does not in any way guarantee skill, knowledge or competence in regards to the work being done. It is also a little known fact that should the contractor fail to pay his/her workers and materials suppliers on the completion of the job, the homeowner will have to pay these people for their goods and services. The only way to protect yourself from this liability is to take a copy of the signed construction/repair contract down to the local city/county building administration and file for a performance bond to be posted by the contractor. The contractor will then have to post the cost of the entire project in the form of a cash bond to cover this liability. This is recommended if you have not been able to check out your contractor or the project is quite large involving subcontractors and other employees.