First of all, you have to know that whether you are willing to share your bedroom and bathroom with some other person or not. If you are afraid of losing your privacy, you should not share your bedroom with anyone. However, if you have no privacy issues or your roommate has good understanding with you as he/she can keep your secrets safe, you can share your bedroom with him/her.
You should also decide that whether you want to live with only one roommate or more. Furthermore, you must know about the friends of your roommates. If he/she has many friends, they may also visit your place at times which can make it really noisy and messy. But, if your roommate has no other friend or he/she has only few friends, then you should not have any problem.
Create an effective ad to find a good roommate. You should mention all the details about your place including the facilities you have in the ad. In addition, you can also mention the requirements which a person should fulfill in order to become your roommate. For instance, you can mention the age limit of the person or any other preference if you want.
Give your ad in any newspaper or on the internet. You can also place your ad on the notice board of your school, college, university or office to find the potential people who can become your roommate.
Meet with the people who contact with you after reading your ad and find the best one out of them.