When it comes to trends, a little goes a long way.
Have you ever seen that girl? You know who I mean, the one who is such a fashion victim - she looks like she's wearing a costume. She's the one wearing cowboy boots with a ruffled mini, topped with a lacy satin camisole and a cropped denim jacket. Don't forget the seven different beaded necklaces, chandelier earrings, and an embossed studded leather belt hanging from her hips.
Don't be that girl. Avoid trend overload by choosing only one to work with, or maybe two if they're subtle. (An aside: if a trend just does not work for body type, leave it on the rack. If you have thick legs, textured, patterned hose with a mini is not a good look.) You especially have to watch it with vintage and historical trends, because if you overload on Victoriana, for instance, you will go from glam to grandma pretty quickly.
Here's an example: let's use the cowboy boots mentioned previously. Now pair them with some classic denim and a fitted white button down. Add a jewel-toned velvet blazer and one or two beaded necklaces - you're good to go.
Let's try another: Military jackets are huge for fall. Pair them with softer, more feminine pieces like floaty chiffon skirts. If you're just not a chiffon person, you can wear these tailored jackets as you would a blazer or denim jacket. An added bonus: these tend to be quite flattering to curves, and the right shape can even create them on a more boyish shape.
One more trend: layered necklaces. It seems pretty simple - get a couple necklaces you like and wear them all at once. However, this one can go really wrong, because you don't want to look like you threw everything but the kitchen sink around your neck. The colors in your necklaces should all be similar, or they should each pick up another color from your outfit. This trend tends to look best with open necklines, and only 3 to 5 (at the very most) strands.
A rule of thumb is to wear one or two more trendy items with your basics. This will tone them down, ensuring that you look stylish without being a slave to fashion. Also, if you know a style is not flattering (because really, only Kate Moss can get away with skinny jeans), put it down. Finally, some trends - leggings come to mind - really shouldn't be worn by anyone. Remember, keep it simple, and you'll look great.