What would be a good sized dram for beginners

One fl.oz in a tasting glass is ample.The Glenmorangie taster (with lid) holds an oz. nicely with room for the addition of spring water or better yet 'Pure Rain'.

Provide cool drinking water at table and after several tastes offer a quality Pilsner or similar natural ale in a small glass: This Ale palate refresher works for me and mine; a small glass is all that's required to get the taste buds back on track! Some say Soda Water works as well but my choice is beer.

Avoid food especially cheese. I did a tasting, once, in Scotland, of Springbanks and home made Shortbread was offered. It was brilliant - the Beer was from the Black Forest but I've forgotten which one.

abunadhman is spot on.

@linusstick a half-ounce pour is perfect. The idea of a "tasting" is NOT a drunk fest. I recommend water (not beer) as the cleanser between pours, and you might consider having an eyedropper available in case anyone wants to add a drop or two to their whisky. Chocolate works remarkably well with smoky and sherried whiskies. Plain bread and some cheeses are perfect for palate cleansers between pours. Take your time; savor and enjoy and discuss each pour.

As the others have said 10-15ml (1oz is about 30ml) should be fine - with 5 drams that's only the equivalent alcoholic content of a couple of pints of beer, so as long as you stretch the tasting out over a sensible amount of time you shouldn't get anyone get hit by the booze too hard. If you serve them in some kind of tasting glass (Glencairn, wine glass, or whatever) then that amount will be easily enough to allow easy nosing of the whisky.

The other thing I'd offer is a communal 'bucket' to pour away unwanted whisky. It may sound like sacrilege, but especially at a tasting for beginners I'd make it easy for anyone who doesn't like a whisky to not feel like they have to finish their dram.

Tell them to offer the glass around first, but having something to dump unwanted whisky in and making it clear that you're not insulted by whisky being poured away can help take pressure of those who don't want to be 'rude'.

@ cowfish, +1.

Also another tip is to have raw coffee beans in a cup (in another room BTW). When switching between two whiskies, a smell of these can clean out your senses due to the raw carbon content. However dont over use it and dont keep it in the same room.

Along with the coffee beans another 'nose resetter' is your own skin - have a sniff of the back of your hand and that does the same thing as coffee does for some people. YMMV etcetc... :)