One of the first things you want is a decent coating on your lenses - and for that you really need one of the big brands - the Nikon HCC is particularly good and the Essilor Crizal is pretty close. Zeiss also does pretty good coatings but their lenses are expensive. A decent coating isn't much more than an average one - £10 or so usually and they are well worth it - I haven't seen a scratched Nikon coating yet and I recommend them daily.
This causes the water to bead and makes it run off the lenses better - makes a big difference.