What is the celebration all about?
Well, fundamentally one should rejoice on a birthday and give thanks and praise to G-d for giving him life.
The birth of a child brings happiness to the parents, to the Jewish people and to the individual, and for this should one give praise.
Ostensibly, birthdays are quite secular affairs, every person (Jew or gentile) has one once a year, in which his "fortune rises."
In fact, in Torah the only birthday singled out for any mention was Pharaoh's birthday!
Nevertheless, a Jew has the ability to utilize his birthday - instead of letting it pass as just another day - he can make it a holiday with emphasis on more Torah and mitzvos.
One's birthday is a time for reflection, when one may "remember and think about those aspects of his life which need improvement and repentance" (HaYom Yom, 11th Nissan).
This should be achieved by increasing Torah and prayer on the birthday, as well as charity and other mitzvos. Add to this a happy gathering of family and friends with the goal of accepting good resolutions and the power of the birthday will guarantee the fulfill ment of the good promises in the future.