The key consideration is where on your frame the jacket sits. For example, the bottom hem will draw a line across your body and could make you look wider than you are.
A trench that falls to the knee is slimming, as is a tailored jacket that sits on your hips. Steer well clear of puffy numbers that bunch and fall right on your waistline.
Fuller figures should look for straight cuts and avoid anything double-breasted. If you're short, steer clear of anything long and think about what you might wear under it.
Whether you want a bright print such as some of these or stick with a tried-and-true neutral, pick up some other pieces that work well with your coat while you're shopping.
A bright pencil skirt looks amazing under a long, dark jacket, or look for a cute blouse to soften a military-style coat. For the real depths of winter, a pastel scarf is a nice way to soften what could otherwise be a severe look.
Buy the best coat you can afford - in a fabric you love - and you'll be wishing away next summer so that you can get it out of the wardrobe again.