Take interest in politics
You will not be able to parody a politician if you don't have political insight. You should regularly read newspapers and watch news channels for an hour or two, just to keep yourself updated about current affairs. Not only should you pay attention to domestic matters, you should also research international politics. Knowing the past history of a politician and his stances is crucial when it comes to creating humor.
Observe body language
In order to make an effective parody, which has the potential to become popular, you have to closely observe the body language of the politician. Most politicians adopt certain styles and mannerisms which are usually peculiar to them. We live in a world of communication these days and you can easily find videos of almost all the major politicians online. Watch them and try to mimic their expressions.
Facial expressions are probably the most important when it comes to political parody.
When making a political parody, you have to adopt the accent of that particular politician. This can be quite a challenging task, but practice can help you become better. Hearing the politician again and again will also make it easier for you to imitate his/her accent.
If you are making a parody for television or theatre, you need to hire the services of high-class makeup artists, who can make you look like the politician you wish to mimic. Your hairstyle, skin tone and the dressing should be like that politician.