If you're having problems matching your records up, there's a few things which might help you learn.

Write bpms on your records
When I started, I used to write the bpms on all my records, so I could guess where the cross fader should be from the difference between the bpms of the two tracks.  Most records don't have the bpms written on them, so you need to get a bpm counter of some sort to do this.  I wrote a bit of software for my Psion so  I could tap the keyboard in time with the tune and it worked out the bpm for me. You can also buy little bpm counters which do this for you.  I'm not sure how reliable the counters you see on some mixers are, never having used them; they probably work better on some tracks than others as it'll depend how clear the beat is.  It's almost certainly more reliable to use something where you tap the beat out and it gives you the reading.  Don't forget when you work out the bpm, you need to have the pitch control zeroed.

So, when you know the bpms of your records, how do you use this to your advantage?  Well, at around 140 - 150bpm, each bpm of difference is equivalent to around 0.7% on the pitch control.  This can be used to get the pitch control for the cueing record in approximately the right place.  Here's an example of how you work it out:

Let's say that the record currently playing has a bpm of about 147 and the pitch control happens to be set at +2.

The next record you want to mix in (the one you're cueing) has a bpm of about 145.

The difference between these bpms is around 2 (147 - 145), which means that the record you're cueing needs to be running about 2bpms faster for them to be matched.  Now, as each bpm of difference is equivalent to about 0.7% on the pitch control, your 2bpms of difference is equivalent to 1.5% (2 x 0.7% roughly) on the pitch control.  As the pitch control on the playing record is already at +2, and the record you're cueing is slower (145bpm vs. 147bpm), then the cueing record needs to be running with the pitch control set at around +3.5% (+2+1.5) on the pitch control to get them approximately matched up.  You'll need to do the fine tuning by ear though!

Headphones
You can try moving the headphone around on your ear - sometimes I find it easier when it's only half on, sometimes not - if you're having problems then experiment!

Also, you could use the headphone cue fader (if you've got one on your mixer) to pre-mix the tracks in the phones.  Although don't rely on this to be able to beatmatch if you're likely to be playing out, as you may not have this facility on the mixers you find in many clubs.

Pitch control
Watch the pitch control position as you're matching.  This will help you develop a feeling for how far you need to move it to get your records matched up.

Dancing
Try dancing while you're mixing.  You might find this helps your beatmatching - and it makes things more fun too.

Volume
I find it easier the louder the music is, within limits of course.  How loud you can go will depend on how friendly your neighbours are.

Two copies of the same record
Use two copies of the same record if you're struggling, as you can give yourself the advantage of knowing whether the record you're cueing up is faster or slower than the one playing just be looking where the pitch control is on both decks.

Channel level meters or beat indicators
Some mixers have LED's which flash in time with the beat of the records.  Also, if you've got channel level meters, you can watch these going up and down in time with the music.

These are all well and good, but I would recommend ignoring them, as you've got to learn to do your beatmatching by ear, not by eye.  Only use them if you're getting really stuck/frustrated.