Recognizing the beat in a song means finding the pattern and speed of the music. If you know how to recognize the beat, you can control all of the other elements of the music.
A beat is a pulse of time. A ticking clock is a good example. Every minute, the second hand ticks 60 times, and each one of those ticks is a beat. If you speed up or slow down the second hand, you’re changing the tempo of the beat.
The tempo and the beat create a sort of skeleton on which you build a rhythm, a pattern of pulses that can be regular or irregular but that always bear some mathematical relation to the beat. The rhythm is expressed in music as notes, which tell you what pitch to play and how long and how often to play them.
Don’t worry. You don’t have to be a perfect metronome of a percussionist to keep a beat. Everything around you has a rhythm to it, from birds to automobiles to babies — and even you — and it isn't as difficult as it may sound to dissect a rhythm to find the beat.
When figuring out how to follow the beat, rhythm sticks (fat cylindrical hard wood instruments) come in real handy. So do drum sticks. If you’ve got a pair, grab ’em — if not, clapping or smacking your hand against bongos or your desktop works just as well.
It is absolutely fundamental that you eventually “hear” a beat in your head while you play music, whether you’re reading a piece of sheet music or jamming with other musicians. The only way you’re going to be able to do this is practice, practice, practice. Following along with the beat in music is something you’re going to have to pick up if you want progress in music.
The easiest way to practice working with a steady beat is to buy a metronome. They’re pretty cheap, and even a crummy one should last you for years. The beauty of a metronome is that you can set it to a wide range of tempos, from very, very slow to hummingbird fast.
If you’re using a metronome to practice with, you can set the beat to whatever speed you’re comfortable with and gradually speed it up to the composer’s intended speed when you’ve figured out the pacing of the song. That metronome serves as the base of the rhythms of the song. No matter what rhythms your hear or play, that beat is a constant underlying factor of the song and should never seem out of place.