My thoughts are.....dress within the season. Meaning....your look should evoke the feeling of the season. If it's fall or winter there should be a look of warmth....grounded warmth. If it's spring or summer there should be an airy coolness to your ensemble. Spring and Fall are transition seasons. So looks can be mixed...as long as the overall feeling leans towards the season ahead of you. For example....it's perfectly acceptable to wear shorts and skirts on a warm fall day....as long as you pair them with fall accessories like boots and/or a jacket. Flip flops and sandles should be put away with your swim suits. No one wants to see bare toes on a wet October day. However, when the sun is shining in March and April....bring 'em out....they look quite cool and carefree on an early Spring day.
Legwear is important too. Over the knee socks and knee highs are great with boots. Dark tights can take a summer dress into the cold and wet season. In the Spring, colored legwear is a great way to lighten up your look after a long cold winter. Snuggle worthy sweaters are great in bright colors too and brightly colored shoes and accessories are a great way to jump into Spring.
Layers are very important in transitional seasons. Long sleeves under short sleeves or tank tops, tights under over the knee socks with your boots and skirt, jackets, scarves and hats...the list goes on. Get dressed in layers too. Make sure that your under layer looks just as nice with those pants as your over layer and your jacket. That way you won't be shy to shed layers as the temperature changes throughout the day.
Summer is all about skin....show it off....use it as an accessory. In the winter you want to protect your skin...cover it up. It's white and pasty for Gods sake! If you don't change your color palate throughout the year....make sure to play with patterns or fabrics. In the summer patterns should be light and airy, in the winter patterns should be bold and more intense. Textured fabrics like tweed or wool are warm and cozy and should be saved for the cold temps.....linen and chiffon are sheer and breezy and should only be worn when the temperature rises.
Just remember....no matter what the time of year....have fun getting dressed. Don't take yourself too seriously....take risks! And....as my Mom always told me...."You're much prettier when you smile!"