Whether you need screening for skin cancer or not will depend on your demographics. If you have a history of skin cancer, if you have a family history of skin cancer, if you have a history of blistering sunburns, or if you use tanning booths regularly, it's probably a good idea for you to get checked for skin cancer.
A dermatologist will determine how often you need to get checked and what type of screening you need. If you have a history of melanoma, likely you'll need to be seen every three to four months by a dermatologist. If you have a history of BCC or SCC, that can be extended to every six months.
It is important to note that not only your moles and the sites of those areas need to be examined but your entire body. This will allow us to look at places that you don't regularly examine and make sure that we note anything that looks suspicious.
Once the exam is complete, your dermatologist will likely use a dermoscope to figure out if there are any suspicious features in the moles that have been identified. Dermoscopy is a great way to determine whether you need a biopsy or not. If suspicious features are noticed, a simple biopsy at the office can determine whether you have skin cancer or precancerous legions, or just a regular mole and will give you a definitive answer.