to avoid vignetting i would suggest using constant av value.
in general, the more settings are fixed, the better (stable) the result.
but, if you want to shoot night&day timelapses then that's whole different story.
lcd turned off - that's a must.
external power supply - also. especially if you're planning to do some long timelapses.
resolution - for web publishing 640 is enough i think, but you could shoot in 1280 or 1600 as well, and then crop/resize images.
always use batch processing for your sequences. i use irfanView + virtualdub combo.
delay between shots - depends on what you're shooting.
fps - 24 or 30. i found videos with 60 fps play choppy on online services.
experiment - make some timelapses, learn, find what suits you the best.
a lot of this has been said before, search
