There are many ways to take snuff...my two most common methods are the ones Huffle talks about, although I never block off my other nostril when snuffing - that makes it way too easy snuff too deeply. Just a few notes:
1. Sniff very, very lightly. The goal is to get the snuff to settle into your nose, not fly back into the sinuses - that's unpleasant at best, miserable at worst. Start sniffing as lightly as you can - if it's not enough to pull the snuff, sniff a little harder until you get it right. Many different grinds and moisture levels mean that every snuff is different in that regard.
2. If you are snuffing a scented snuff (ie, anything more than just tobacco), it can help to hold the snuff in your pinch for a few seconds before insuflating - not because it makes it easier, but because the warmth from your fingers will help release some of the essential oils used to create the scent, giving much more flavor when you take it in.
3. You WILL sneeze, especially at first. Sneezing does not mean you've done something wrong.
4. Carry a hankie. You'll find that some snuffs take longer, others no time at all, but they'll give you the need to blow your nose at some point.
As far as what snuffs to try:
Early on, you should be looking for medium grinds with a fair bit of moisture. These are the easiest to take and the easiest to have settle where you want them. AVOID anything that's called "toast" or "scotch." These are very fine and very dry and most people need to have some sort of technique behind them before trying to tackle them. To that end, also avoid ordering anything from the Toque brand. Toque makes some EXCELLENT snuffs, they are will priced, have a wide range of scents and are all-around an excellent product...the trouble is that the grind/moisture make them a little trickier for newcomers.
As far as "user friendly" snuffs, I find that it's hard to go wrong with anything made by Viking. Also, if it sounds appealing, Sam Gawith Black Coffee (or Snuffstore Cafe Noir) are both easy take and very nicely scented. For something sweeter, you could look to anything made by Bernards. If you like - or you think you might like - menthol (not my cup of tea), Poschl makes some incredibly popular snuffs that are well known for being super easy to take.
I snuff at least as much as I smoke these days, so if you run into any questions, definitely post here...I'm no expert but I'm happy to offer any advice!