What you wear to work is probably the most important part of your wardrobe. Your appearance could be the difference between getting that promotion and being stuck in the same position forever.

But what is an appropriate look and style? Check out these work wardrobe faux-pas to make sure you don't repeat them.

1. Showing underwear

Showing bra straps or even the whole of your bra through a light blouse will encourage your male colleagues to see you as a woman rather than a professional. If you really want to wear a sheer blouse, wear a nude-coloured camisole underneath.

As for slips, one length does NOT fit all. Buy slips in several lengths and in the colours you wear most often. You want to mute the sheerness of your garment - and not draw attention to the colour of what's underneath.

2. Wearing the wrong colours

The lime green or hot pink that's all the rage this season may look fab on the catwalk but awful on you. Don't waste your money on clothes that make you look pale or washed-out, either. Plenty of department stores have personal shoppers who offer free style counselling, so why not get some tips from the experts?

3. High heels and scuffed shoes

Shoes should be comfortable to walk in, especially if you're on your feet for long periods of time. It's not worth blisters just to look that extra bit special. The highest heels women should wear to the office are two to three inches.

Check shoes regularly to make sure they're in good condition - many department stores and stations have heel bars where you can drop in at lunchtime.

4. Wearing too small a size

If it doesn't fit, don't wear it. High street clothes will never look fitted so it's worthwhile investing in a tailored suit. A well-made suit will conform to your body shape and posture and retain fit and shape for many, many wearings.

5. Skimpy attire

We've had some hot summers lately but there's no excuse to look like you're off to the beach. Choose clothes in light colours and fabrics that stay cool, such as linens and lightweight wool. The Trades Union Congress (TUC) have said employers should follow the Japanese Prime Minister, who urged his country not to wear jackets and ties during summer.

Wool can be worn all year round and a light-weight suit with a partial lining is perfect for summer. For linen, choose blends with cotton or silk to avoid too much creasing.

6. Underarm stains

You may have to try a few deodorants to find the best one for you. If you perspire heavily or need a surefire method to prevent stains, consider using dress or jacket shields.

7. Too much cleavage

If you show off your body, you will simply encourage your male colleagues to look at you as little more than someone they would like to sleep with. This may boost your ego but it certainly won't boost your career opportunities.

8. Out-of-control hair

Wild hair just doesn't look professional. Women should invest in a good haircut and styling products to make hair easier to manage. Men should keep their facial hair well-trimmed or, better still, be clean-shaven.

9. Being too casual

Last year, Barclays Bank reportedly sent staff a memo stipulating that jeans, shorts, flip-flops, strapless tops, sportswear, T-shirts or trainers would not be tolerated in the workplace.

How should you define dress-down Fridays and smart casual? If you really want to wear jeans, make sure they're clean, neat and fit well - dress them up with a tailored shirt and jacket or blazer.

10. Too much jewellery

An employee of British Airways (BA) took them to court for refusing to let her wear a cross. BA's policy is that personal items of jewellery, including crosses, may be worn but underneath the uniform.

Wherever you work, jewellery should always be kept to a minimum - keep it simple, like a watch, dainty necklace/plain cufflinks and a ring.

The saying "Never judge a book by its cover" doesn't apply in the workplace. Where else in life can the clothes you wear have a genuine effect on your future and how you're perceived?