First, it is not absolutely necessary to start or finish on the 1st note of a scale when practicing with a metronome. Consider, you can simply play one or two notes over and again. Or strum one chord. Also, it is not necessary to stick to 4 counts. Try 2, 3, 5, 6, 7. Anything is fine as long as you are playing in time with the pulse of the metronome.

Make sense?

To address your question:

Originally Posted by: kjproWhat I mean is, lets say I'm playing the Gmajor scale. I start on the one (1) count by the time I get back to the low G to restart the scale, am either infront or behind the metronome one (1) count. This happens especially when I try the triplets.
How do I correct that so that I restart in perfect timing? And how will I know?

If you want to play a certain amount of notes and have it perfectly square with a certain time signature or rhythmic group of notes, then you have to plan ahead for these things to coordinate. You need to factor in every aspect to consider.

For example, if you want to play:

1. G major scale - one octave
2. One note at a time.
3. Ascending.
4. Quarter notes.
5. 4/4 time.

Then the notes will line up against the rhythm like this:

g-a-b-c-d-e-f#
1-2-3-4-1-2-3

As you can see, if you repeat this pattern, you will get a "g" note on beat 4!

So you add a "g" at the end.

g-a-b-c-d-e-f#-g
1-2-3-4-1-2-3- 4

Now things will square up. :)

Another example.

1. G major scale - one octave
2. One note at a time.
3. Ascending & descending.
4. Eighth notes.
5. 4/4 time.

Then the notes will line up against the rhythm like this:

g-a-b-c-d-e-f#-g-f#-e-d-c-b-a
1-&-2-&-3-&-4- &-1- &-2-&-3-&

Oh no! Again, you get a "g" note on beat 4!

So you have to add something. Double the "g" in the middle and at the end and things will square up again.

g-a-b-c-d-e-f#-g-g-f#-e-d-c-b-a-g
1-&-2-&-3-&-4- &-1-&- 2-&-3-&-4-&

Make sense? :)