I'm a complete beginner to After Effects and Premier Pro. When I typed directly into After Effects and then did a "Best Settings" render my text looks a bit pixelated. Is this the best quality AE can do or would it be better to import the text in another format for high quality? Transparent TIF for example? Is there another thing I should look at in the render settings to ensure the type renders crisp?
The quality of the text is going to depend on the quality of the font. There are two types of fonts, bitmap and vector.
Bitmap fonts basically have pictures of each letter and information about how they should be spaced, each font size that is officially supported has its own picture. Vector fonts are a mathematical description of the characters and can be resized smoothly.
If you are using a bitmap font and not using a sufficient font point size, then you will get a pixelated image. Try using other fonts and/or adjusting the point size to find one that isn't pixelated. It should be perfectly possible to render fonts smoothly in After Effects directly.
I suspect you have the view window set at less than 100% scale. Your quality setting should match your view screen scale. For example, if your view screen is at 50% you should set the quality to half. If the screen is at 49% or 51% the text will look jagged (aliased). The Auto setting on the quality drop down is useful to keep the closest quality setting to your scale.