You may be curious about your next birth if you believe in it. It is true that you have to birth again if you have not completed your jobs and not fulfilling your expectation. The reason is that if you could not achieve your dreams and expectations in your present birth, then you will return in the next birth. However, you had to vow yourself to return at the time of your death. Of course, you have to expect it desperately. So some points are discussed for your curiosity.
If you do good karma and could not fulfill your expectation, then you can return in this world. But first you have to do the good jobs and then you can expect your return again. If you do good deeds in your present birth, then you will again born in a better place and environment than you are now residing in your present condition. However, if you like to born again for taking the revenge on someone, then you have to born in the violent condition and face the sufferings. Even, if you are evil, then you have to do at least a good deed in your life. So that you can have a chance to born again in this world. Your rebirth process will solely depend on you how you can see the proceedings in your favor.
If you have not completed your jobs within your lifespan, then you may come back again in this abode. It is better to complete before you leave this world. Otherwise, you have to born again to complete it. It is observed that every rebirth is painful. The reason is that the spirit of your body generally does not like to enter into a fleshy substance again. Therefore, the spirit may play hide and seek in the process of the rebirth. Sometimes the spirit can enter into a wrong body. It will depend on how the supreme power can control it. Always try to die with a wish that you can do good deeds in your next birth.
Always try to limit your expectation to a limit in your present birth. You should expect the achievable target, which you can get it in your lifespan. However, if your expectation is beyond your reach, then you have to born again with your incomplete wish. Actually, it is not desirable at all.
Therefore, your next birth will be in a way that it can be painless and comfortable. Therefore, in your present birth, you should always try to complete your wish and deeds so that you will not require to birth again.