This forum first and then all the ususal trade magazines, reps,google. The reps are particulalry good; when they tell you of a new way of switching or connecting etc. then you know that there has been a development and can go and look at other manufacturers. As a non-electrical example; I saw a fender telecaster this week with a very interesting method of connecting the strings via a trap door in the locking nut and a ratchet mechanism. Never seen it before but I happen to be off guitar shopping today and am now ready to look at that on every model and see what the alternatives are.
But in my case most of keeping up comes from being half my time on the tools and out there seeing a variety of installations. It is very easy for an engineer to get stuck into specifying what he knows and is comfortable with, but actually having to inspect or install something new is a sure way of appreciating how things are developing. It's good to actually get your hands on something and see it in action.
Take the megger MFT1730 for example.....
Bought mine on the strength of the marketing and gadgetry but should have tried it out first.