Right, this is a guide that badly needs addressed, considering the sheer number of roleplays I've seen lately centered around small children lately. Plus, as a person who has regularly worked with children from ages 2-13, I can tell you now that those little buggers are just as complicated as an adult or teenager.
I'm going to have to break this down by age range in order to cover this adequately, but I'll try and do my best to put up I'll cover some general information in this first post.
Abilities
Why A Child is Not An Adult
Child are not little adults, and I feel as if I need to address this. Depending on the edge, your character may or may not be able to to certain things. They will act certain ways and have certain abilities.
Despite the very RARE exception of a child prodigy, your child character is not likely to be able to take down anyone twice their size and weight, or be able to program a super computer. Most children are not expert cooks, or experts at anything but having fun.
Now a child can be good at something. But to be an expert takes a lot of experience. Keep this in mind.
I'm not going to go in-depth on this particular issue, but I will say a few more points.
Watch the vocabulary of your post. When you were seven, did you know what words like 'precocious' or 'doddering' meant? Of course not. So your child should probably keep to a simpler vocabulary, depending on age and intelligence. More on this later.
Depth of Character
Hey! I'm a Person Too!
Don't overplay that childishness! As tempting as it can be, to make you child cute and adorable seeming through sheer childishness, this doesn't work out well. If anything, it backfires. A common problem I've seen here is what I call the Speech Impediment Sue. SIS gets discuss soon enough though.
Keep in mind your child's age, alright? A six year old will not act like she is three. Nor will a twelve year old act like she is 5. That would have been mocked out of them quickly. Keep in mind the differences. A twelve year old is going to have a very different range of likes than a five year old. (The Power Rangers vs Spy Kids, for example.)
Common Complaints
Speech Impediments and Your Character
Hello Speech Impediment Sue. Let's talk shall we?
SIS: Okay, lady!
So, how old are you Sue?
SIS: I'm six an a half! (Small children often love adding fractions to their age.)
Really? Sounds exciting!
SIS: Wewwy! Hey do you wike puppies an kitties!
Sure, Sue. Hey, can you say 'Be very, very quiet, I'm hunting rabbits?'
SIS: Be vewy vewy quiet, I'm hunting wabbits
I think that about proves my point on Speech Impediment Sue, don't you? To demonstrate exactly who you don't want your poor hapless child characters to be, let me show you two lovely pictures.


Here's a few pages with some Good Advice to tide you over.
Child Narrators In Adult Fiction
On Writing Child Characters for Adults Gary Murning










