>> Basic beat mixing in detail, using your Technics turntables properly:
The best way to learn beat mixing from the beginning is to try to get two identical records. Two identical records won't go out of time if the pitch is set the same. If you don't have two the same try listening carefully to some of your tracks and pick two that have clear rhythmical sounds. This would mean a big bass kick sound at the start of a bar and clear snare sounds or high hat sounds marking the other beats in the bar. You should also try to select tracks that start straight into beats and not strings and other ambient sounds.

>> How to do your first mix step by step:
To start, first set one record to play and "cue" the next record up. Make sure the cross-fader is over to the side that has the playing track so that no sound comes out of the speakers from the cue channel. Cue the new track by putting the needle at the start of the record at letting it play before stopping it at the first sound. (this cue channel should be coming out of your headphones). The turntable platter should be rotating underneath the record now. Here is a picture showing you how to hold the track ready to drop.

This first sound you grab like this should be the first beat of the first bar of the track. You should hold this beat so that the sound in the groove (in the vinyl) is underneath the needle and when you move your hand the beat sounds slowly through your headphones. The tricky part now is to start this beat at the same time as first beat of the bar of the currently playing track. If you do this correctly the beats should overlap as both tracks play. Dropping a cue track in time with the track playing out is not easy and does require some practice to get the hang of.