There are no set rules on clothes, every photographer has different preferences, but it's important to have a range of tops to give them choice of what to shoot with.
Remember with clothing, if you stuff your tops in a bag they will look like they were stuffed in a bag for the shoot. Bring them in a suitable bag or suit carrier if you can – even the t-shirts, it will make a difference, and give you one less thing to stress over.
Think about some solid colours
Try to wear colours that compliment your skin tone. This will help accentuate your natural features. Always bring some neutral tones and dark tops as a choice, but remember you are having colour photographs taken, why not bring some vibrancy to the shots.
What is your neck like?
Look in the mirror and study your body. Is your neck short or long? As a general rule, V-neck and wide scoop neck clothes will lengthen the neck; tighter round necklines and high collars will shorten it and feel stockier. Take a selection of both if in doubt. Think about how closed off you want your clothing to feel.
Beware of patterns that are too distracting
There is a fine line between characterful clothing and focus pulling. Some light patterns and big chunky patterns are fine and can be great for character shots sometimes, but if the first thing people notice is the top you are wearing, we've gone wrong! Try and avoid heavy logos as well, as they can be distracting.
If you always wear glasses definitely shoot with them on, although sometimes they can distract away from your eyes which are the most striking part of your headshot, so you may wish to shoot some without also, take contacts if you have them. If you have multiple glasses, think about the ones that have non-reflective lenses in, you will notice they have a green/blue tint when you look at them, this is a big help to your photographer.
Don't just think single layers, t-shirts under shirts, suit jackets, cardigans and take a coat or jacket that are contrasting, layering them over another top might add something a little different.
Keep it personal
Wear clothing that makes you feel good and you are relaxed in. Being comfortable will show through in your photos. If you have a top that people have complimented you on, it's a good start.