Ok, sorry Ive been away for a way guys, times were hard but exams are done now
I usually do this exercise to warm but I used to do it all the time and it can build up good strength and co-ordination. Play the chromatic scale, every note in the first position. To cut a long story short and to spare you theory: On the E string, you play open, 1st, 2nd, 3rd THEN 1st, 2nd, 3rd, 4th, THEN 2nd, 3rd, 4th, and OPEN A THEN 3rd, 4th, open A, 1st (On A) That may sound complicated but its very simple to understand yet annoyingly hard to play fast when you first start out. So you play 4 notes each time. Start on E (which is just open E) and then play the three semitones that follow it. Then change root to the next note, F and play the three semitones following that. You continue until your last 4 notes are the first 4 frets on G string. If you didnt understand that last bit then ignore it and re-read the first bit
Remember, you never go above the 4th fret on any string, you move on to the open of the next string, thats what makes it tricky.
Keep practicising that and you will build good strength and co-ordination.