You can do the modules in any order, though we recommend 1/2/3 or 1/3/2. Most people submit their work for each module as they finish it, though as all three modules feed into and support each other, you could do all three courses and only then submit work. It is possible to do different Modules at different centres (though we obviously think you should do them all with us).
You can submit Delta work (do the exam (Module One), submit your coursework portfolio (Module Two) or submit your extended assignment (Module Three)) on the first Wednesday of December or the first Wednesday of June every year.
Delta is a considerable commitment in terms of time and effort. Quite how much time or effort will vary according to your background (a first degree in education or an ELT Masters usually makes the academic research and writing aspects easier), your experience (the wider variety of situations you have taught in and the greater the range of different course books and resources you have used, the more ideas you will have to draw on in Module Two) and your developmental pathway (if you are in an institution that provides regular in service training and observation some elements will be more familiar).
Having done a CELTA helps prepare you a little and having done an ICELT helps a lot. Different Modules have different practical requirements in terms of how much of the Module can be completed on line, to what extent they can be completed intensively and where you need to be teaching (or even whether you need to be). See individual Module information for details.