The gentleman's scarf is generally an accessory that only comes out when the mercury plummets, often joining the usual suit and tie combination.
With that approach, you can stick to entry level scarf tying. When your scarf is for practicality and not just fashion, the key thing to remember is that looping is better than tying. If you tie a scarf when it is cold, then you use up extra length that could be keeping your neck warm. Unless you have an exceptionally long scarf, simply wrap it one or two times around your neck. Let the ends hang at different lengths. Tuck them into your coat for extra warmth if you live some place especially cold. That is the simple side of tying a scarf.
Now, if you are adding a scarf with more emphasis on fashion than comfort, then these how to's on tying your scarf will be simple for that approach, too. In the how to, scarves have been broken down by style and length of fabric. That way, you will know how to tie your scarf no matter what comes your way.
Thinner fabrics allow for fancier knotting, but the knots take up the fabric. When it comes to heavy scarves, knots can quickly grow out of proportion to the rest of the scarf. There is a time and a place for a big knot, but it is not with flimsy fabrics. With thinner material, your scarf comes either in a roughly square shape or else in a generally longer style. The square shaped scarf allows for a number of knots.
To tie a scarf with style, consider folding it diagonally and tying it like a neckerchief in front or back. Be careful not to make it look like a bib or bonnet and you should be good to go. For longer scarves, there are a couple of styles that will only fit a thinner fabric. One of these is to tie your scarf like a bow tie. Knot it like your shoe laces, but be sure that more hangs from the loose ends than from the knots. You do not want a flop eared dog hanging on your neck.
Another option that works best with thinner fabrics is to loosely wrap your scarf a few times, leaving one end significantly longer, but usually no longer than your hip. Tuck the shorter end out of sight. It leaves an air of mystery. Also, good with lighter scarves, but okay for thicker ones, is to twist it length wise until it looks like a piece of licorice. Loop it and knot it around your neck. This works especially well with solid colored scarves, lending flair to the single tone.
Now, most ways to tie a thicker, longer scarf will often match a thinner scarf as well. The same is not true in reverse, though, so with thicker fabrics, two considerations prevail, which are the loops and knots. A simple slip knot is always classy, as is a one pass wrap. When wrapping the scarf around your neck, you achieve the best look by wrapping both ends over and around the back of your neck. You can then let them hang or else loosely knot them.
You can vary this and the slip knot by aiming for a larger knot, but if that sits on your throat, it looks like you swallowed a watermelon. Slide it around to the side of your neck for more accent and less fruit market. You can also go minimalist or hog wild on looping. It is completely acceptable just to drape the scarf around your neck and let it hang. As well, you can loop it multiple times. With several loops, keep them close together if it is cold and knot it at the end. Be sure to leave some of the end hanging. If it is not cold, then you do not want to be hugging your neck quite so tightly. Drape the loops in various lengths.