Hair grows, leaving unloced hair at the roots of your locs, which can be very frizzy (especially at the beginning stages of locing) and leave loose hairs unattached to any locs.
There a few choices to take with your new growth:
* FREEFORM
Some people like their locs to form naturally, so the new growth is left to loc by itself and no other method is used.
*WRAPPING LOOSE HAIRS AROUND THE LOC
This was the method I used until now -taking the new growth and wrapping around the nearest loc. For a more secure wrap, thread the root hairs through the loc, wrap around, thread it through...keep going until all the loose hairs the root are wrapped around the loc. I found this a good method to get my hair to loc in a cylindrical and uniform way. I would recommend it to anyone at the beginning stages of locing -for the first year. Do it after every wash or when you just want to neaten the roots. It doesn't make the loc thinner like twisting does.
*FINGER LATCHING
This technique is what I have recently been using. The technique is:
Part the root of the loc, take the end of your loc and thread it through the root parting, then pull the loc down. I found it to really tighten the roots. However, it does change the loc texture (so I read), therefore I plan to use this technique only once a month and wrap during the other times.
I haven't mentioned twisting locs as I feel that this is a bad thing and eventually leads to breakage.
Try all the techniques and see which one works for you.