I find that a lot of developers stick to one development methodology. Now while I personally like development methodologies as they have been created on best practice and proved empirically in real world projects, you need to learn to use the best tool for the job. I tend to mainly lean towards agile development.

The main development methodologies are:

Agile

Agile started from the agile manifesto and is designed to deliver the software your customer needs when it is needed. Unlike waterfall it allows you to react to the inevitable change in requirements even if they are late in the project. It is a set of values that cover planning, designing, coding and testing. Branches of agile include extreme programming (XP) and scrum.

Rational Unified Process

This is an iterative software development process developed by a IBM. It is not a rigid process but more of an adaptable framework that is tailored to the project and organisation.

Waterfall

This is a sequential approach to software development and typifies the Microsoft dominance of the 90s. You move from one phase to the next, as you do the previous stage is set in stone and cannot be changed. E.g. when you move from requirements to design you flow down the waterfall and cannot go back up.

I have never worked with waterfall but I have experience of the rest and will be sharing my thoughts over the next few days.