The most important thing that you need to do in order to remain more cheerful is to become more comfortable in your skin. You should recognise your unique traits and be proud of them instead of hiding them, fearing that the people may reject you or find you weird. You need to understand that nobody is perfect and people will not judge you on your imperfections.
If you see someone in need, try to help them out. You need to understand that not everyone is blessed with the same privileges as you. There is a lot of poverty and other ills in the world. You cannot possibly eradicate them, but you can do your share to lessen them and help many under-privileged people. You will most likely run into needy people in your own area. If you live in a posh area, then do your bit for humanity by donating to charities, doing volunteer work at old-age homes and NGOs, etc. You will attain inner peace by helping others.
Whenever you are going through a tough time, try to remain optimistic instead of letting the gloominess take you over. Remember that everything becomes okay in the end. If it is not okay, it is definitely not the end. Remaining positive will give you the necessary vigour to successfully make it through the tough time and allow you to hold on to your cheerfulness.
Listening is just as important to remain cheerful as talking. While a happy person has a lot of good things to share with the people around them, there are a lot of things that people have to share as well. Learn to patiently listen to others. You will get to learn a lot from their experience.
Take care of your health. Your mood depends a lot on how well you are feeling. Eat healthy, exercise regularly and get plenty of sleep at night.