Acquire beat making software. Such programs can be bought or downloaded from Image Line, Acid Pro, or Pro Tools. This software includes a wider variety of effects, crisper sound, and is much more professional than freeware programs.
Set a tempo. This can range from under 50 to over 100 beats per minute. Sing the lyrics and set the tempo to the speed of how the song is sung.
Create a sound to the tempo. This includes a hi hat, bass drum, or snare. Experiment with different hi hat and drum sounds until you find one that fits the mood of the song.
Add additional sounds and create a loop. For example, a fast-paced song would use rapidly hitting hi hats with a bass and snare sound between. Adjust the tempo if the loop sounds too slow or too fast. Sing or rap the lyrics to the loop. Add or remove sounds from the beat until it fits.
Add instrument sounds. Choose a key such as a major or minor, depending on the mood of the song. For example, use minor keys if the song is sad or major keys if the song is happy. Repeat a melody over the primary drum beat and add notes to fit the song lyrics.
Add layers of effects. Insert keyboard and other instrument sounds to create variety. Create tension at the end of the verse and lead up to the chorus. This should employ a repetitious melody that is memorable for the listener.
Edit the lyrics. Remove any unneeded words so that each line fits the beat. Add extra words and syllables as well.