Each dreadlock is individual.  Sometimes when we view the Dreadlocks of others they seem to be perfectly cylindrical...but that's from afar.

The information contained in this section is for those who have reached maturity.  If you're trying to keep your dreadlocks neat looking or uniform and you have not yet fully lock'd, patience is the answer to your question.

Immature dreadlocks are unpredictable and chances are your dreads will become more uniform, cylindrical with regular maintenance and more importantly...TIME.  So aside from following the normal maintenance tips, try not to fuss too much over the frizziness or structure of your locks.

Mature Dreadlocks
It's not uncommon for people with mature dreadlocks to have several dispersed throughout their mane which have kinks or knots in them. 

Sometimes these knots/kinks can be smoothed out by focusing your finger-twisting efforts on the kink'd portion.  With regular twisting you maybe able to smooth out the bumps and straighten the lock.

Others complain of "flapping" or flattened dreads.  This usually occurs from neglect (although some people actually encourage flapping).  Again, by focusing your palm-rolling efforts on the flattened locks, you maybe able to encourage them to take on a more cylindrical shape.  Keep in mind however you have better results when you address this situation early on.

Another way to deal with flattened dreadlocks is by using rounded beads.  The idea is that the round beads will force the locks to take on a less flattened shape but this technique doesn't work for everyone.

Frizzy hair down the length of the dreadlock is also common for dreadheads.  Basically this is when the lock continues to look fuzzy structurally.

If you've reached maturity and find that the length of your lock is fuzzy, you can handle it a few different ways...

Leave it as is.  The frizzies don't necessarily bother you so if it ain't broke...

Palm-roll or braid the frizzies down and around the dreadlock.  This basically means you continue with regular maintenance in hopes that the frizzies will adhere to the dreadlock or to give an overall neater appearance.

This method is mildly effect because once you shampoo, the frizzy hairs that are 1/4 inch or so in length will just pop right out again.  This is typically why we palm-roll.

Finally, clip them.  If you've ever had your hair braided with extensions, one of the final steps that many braid stylists do is to take a pair of scissors and trim away the random loose hairs that poke of the individual braids.

It's kinda silly when you think about it because if your hair is 10 inches long and she's cutting 5 inches down from your scalp, she's cutting YOUR hair which may cause it to be uneven when the braids are taken down.

Although it may not be the smartest move with braids, this technique is ok for dreadlocks because it's not like you ever plan on taking them down...nor would you exactly be able to.

Basically, you trim the loose hairs along the sides of each individual lock.  Be sure to start trimming about 2-3 inches away from the dreadlock root.  You don't want to accidently snip the hair that connects the dreadlock to your scalp.