Xiphias

This Guide is my personal perception of how you make a good avatar. What I consider a good avatar may be different from what another does, but this is just intended to give a vague idea.
From my point of view there are a lot of different aspects combined to make what I would describe as a good avatar. Some of these you might like to consider are:
Colour Scheme
(This is basically having at least one or more colours in an outfit that are well co-ordinated, i.e matching, or of a similar shade, or various shades that compliment eachother.) A very simple example of a colour scheme (in this case using just brown) is shown below, along with an example of something with no colour scheme:

Flow
(This is a way of arranging your items so that they look nice together, and have a 'flowing' appearance.) An example of a very flowing outfit is shown below, along with one with next to no flow:

Originality
(Have you seen your outfit/a similar concept on someone else a million times before? Or are you using a full set? In that case your outfit is not original.)
An original outfit should be something that hasn't really been seen a lot before, maybe with a new type of layering, or an interesting item combination. An example (by Hezyfaerie) of something original is shown below, along with something completely unoriginal:

Theme
(This is creating an avatar which actually attempts to convey a particular look, for example 'Pirate') At times if you have a very strong theme then other aspects such as colour scheme can be looked over, but the best avatars combine the two.)
An example of a great themed outfit is this one, (by BarbieSlave) based on Cupid:

It's very obvious what the theme for this one is,
as she incorporates lots of items which convey the
theme well, like the arrow and the fairy wings for example.
And there we have it, Colour Scheme, Flow, Originality and Theme.
The four components which I feel are necessary to create a good outfit.
I hope this Guide has been useful (particularly if you were directed to it by me)
but I would also recommend reading the AT 101 Sticky for more handy info on avatar making and AT in general.
And thankyou to Barbie and Hezy for letting me pinch your outfits, hope you don't mind. ninja
All Credit goes to Xiphia for makeing this great faq.