Not long ago, I witnessed a guy trying to get into a pub where he was barred, and I thought that now and again it would be useful to have an outfit to conceal your identity. I mean, if the Queen can do it, so can we!
Assuming you don’t want a wardrobe full of misleading clothing, the most useful outfit is going to be suitable for all seasons, locations and activities that you might reasonably do.
And if you honestly don’t want to be recognised, as opposed to putting on a floppy hat and big sunglasses, this is going to be the hardest outfit for you to wear because a little part of you will die inside when you look at yourself in the mirror.
Follow the Queen’s example, and don’t dress the way the people looking for you will recognise. If you look at the pictures in Unity Blott’s article above, you’ll see that in “public”, the Queen wears boldly coloured fitted clothes, matching hats, low heels, with distinctive jewellery and visible makeup. In “private” she wears looser clothing in neutral colours, headscarves, flat lace-ups or wellingtons as well as glasses and more natural makeup.
Or another example is Superman’s dowdy, clumsy alter ego, Clark Kent.
Both of these characters are so convincing in style and manner that it doesn’t occur to anyone that she is the Queen or he is a Superhero. Consider developing your own alter ego with a different character and mannerisms. Use this person to guide your clothing, accessory and hair choices.
Wear the kind of clothes that your alter ego would wear, (ideally opposite to you) but at the same time, don’t make them so distinctive that they stand out in your surroundings causing people look at you again. They may look more closely at your face in an attempt to determine what kind of person wears that outlandish get up. Bonus points if the colours you choose change your skin and hair tone.
If you think you might need to change clothes between entering and exiting a building/train/park, consider clothes that can be layered or worn inside out so that they look like different clothes.
People who know you well will instantly recognise you by the way that you move so you might find it useful to change your gait with something lumpy in your shoe. You could also change your height with lower or higher shoes.
You could add something distracting like the hat or glasses, but they won’t work unless the rest of your disguise is in place. Coloured contact lenses might work better than glasses.
If you think you can sustain it, consider giving yourself an accent.
If you choose to wear a wig, make sure it fits well and is securely placed. Alternatively, if you are prepared, try a semi-permanent dye or crayons/chalks. Change your hairstyle by parting and styling it differently.
Wear more, less, or different coloured makeup. If you’re good at it, you might go as far as adding beauty marks, bruises, skin conditions, putty or fake noses. If you’re less good at it, changing your eyebrow style and contouring your face will probably be sufficient.
It seems that adequately concealing your identity takes some thought and preparation. It’s probably not something you can do when you are drunk and trying to get back into the pub (unless you are an excellent actor).
Would this plan meet your needs? Have I missed anything you think is more important?