Beat mixing is the primary skill that separates newbie dj's from  professional dj's. Beat mixing is far more important than any other dj skills.  Regardless of the music type you are blending your number one concern is a even transition that's always on beat.

Mastering the basics of beat mixing will require much practice. A serious dj will practice up to 3 to 5 hours per day.  Learning your music and mixing all possible blends will give you an upper hand when you have to spin for an audience.

Whatever your preferred music styles it's important to practice them all.  And don't ever throw away or delete any music from your music resource center.(record crates) You never know when you are going to need the old music.  It never surprises me when old songs regain popularity.

Before you can mix anything you need to know the required equipment. Once you have all the equipment you will play a song on turntable #1 outputting the sound through the speakers.  Next use your headphones to listen to the record that is not heard through the speakers. Your pitch control should be set at "0". It's best to start off with two of the same songs. (See basics of djing)This way you can know for sure that your mix is on the beat.

Once you have turntable #1 playing out loud through the speakers, and turntable #2 cued in your headphones, try to synchronize them together so it sounds like one record playing.  If you do it correctly you will hear a phasing echo sound. Eventually you should be able to remove the phasing echo at will.

Once you can master mixing the same record, then you should attempt to mix 2 different songs.  Be sure that the bpm (beat per minute) of the songs are relatively close. Your pitch control will only speed up or slow down a song so far. And plus you don't want your music to sound like mickey mouse music.

If you don't have a metronome than you can figure dance and house music will be between 115 bpm's to 150 bpm's.  Hip-hop and rap music will normally be at about 75bpm's to 110 bpm's. Of course this is the rules. There are many exceptions. The more you listen your music approximating the bpm's will become second nature.