When I went to Amsterdam a few years ago, I managed to wander through the red light district without noticing anything to do with sex, I went past many cafe's without noticing any drugs. They were there, I was just blind.

Nope, though I did get some novelty sunglasses which had a green holographic smiley in each lens. They drew some stares.

I have a workshop to attend to at the same time, so I probably don't have time to meet up with anyone (although the workshop is in Amsterdam - which reminds me, I still need to prepare for the workshop). I may be able to squeeze something in on the 26th, but no promises. Remind me a couple of days in advance.

Depends on what you like to see. What I can recommend you to do is take a boat tour. You'll get a very quick overview of the city and a general idea on where you might go.

As anywhere, beware of pick-pockets. Check in advance when the last trams leave from any particular location (usually around midnight) and where the night bus stops are.
Above all, make sure you don't wander over the cycling lines. Most cyclers here (myself included) are so fed up with tourists who don't realise that they're on a cycling lane that they simply ignore the fact that they're there and run them down.

As for coffeeshops, do as you like with those, but if you decide to go there, make sure you don't end up taking enough drugs for a lifetime in one shot, as some of the tourists (especially British tourists) seem to do.

http://www.moviepostershop.com/item_img/hum201.jpg

I don't know the hotel, but a hotel at that location sounds like it would be expensive...
Near to the centre is a relative term. It's about half way from where I live (which is fairly close to the outskirts of the city) to the centre, which isn't too bad, and you can probably cut through the park, which can be quite nice (but I don't recommend it at night if you're alone). Tram connections from there to the centre should be very good, but I don't know about the night bus. Then again, it shouldn't be more than half an hour walk from there.

It's not a prerequisite; I know people who smoke (or smoked) weed but have never smoked tobacco. As pubs go, Coffeeshops aren't great. The smell is rather nauseating if you don't like it.

I can make it. Somebody (more knowledgeable about Amsterdam than me) pick a nice quiet pub to meet and have a few drinks. Saturday 25 would be most convenient for me.

I knew about the red light area in Amsterdam, but I had a great laugh, when I saw a hotel named "Multatuli". Forgive me, all Dutchmen here, but it is a bit bizarre. It is Finnish and it means... well...

"I ejaculated"

Well, I usually don't suffer...

Van Gogh has a museum there, if you're into that sort of thing.

It's hideously expensive though.

The Irish pub I was thinking of is on the Rokin and they very conveniently have a website: http://www.thetara.com/index.php?page=location
What do we do for the time and how to we recognise oneanother?

How about tinfoil hats?

I'd prefer a bit earlier, or I'll just sit around, waiting. Maybe 19.00?

Ok, that is a good reason :p. So 21.30 then.