Tip #1 - clothing.
Without a doubt, the one thing that ruins more portraits than anything else is uncoordinated clothing! Keep your clothing choice subtle...
meaning non-distracting.
You do not want your clothes to take the viewer's eyes away from your face.
Tip #2 - avoid designs and logos.
  It is strongly recommended that you keep your outfits as plain and as undistracting as possible.
  Logos and funky designs might look chic to the eye, but in a portrait, they will be very distracting.
  Remember, you do not want anything to distract from your face.
  Tip #3 - Consider long sleeves!  Because your skin is the same color as your face, having your portrait taken in short sleeves - or even worse - in a sleeveless shirt - will take away the attention from your face to other skin that is showing.
  In addition to this, long sleeves can hide things that you might not want in your portrait such as tattoos and scars.
  Plus, in the event that you might have a little extra in your arms, the long sleeve will hide this too.
Tip #4 - Wear darker colors.
 By wearing darker colored clothes...
from your shoulders to your feet, you will actually look slimmer!  No kidding.
  The reason this happens is simple.
  Unlike with lighter colors when the eye can see the lines and edges of the clothes...
this won't happen with dark clothes.
  Call it an optical illusion if you must.
  Jet black clothes in a portrait make you look really slim if the photographer knows what they are doing.
  Not only does the wearing of dark clothes make you look slimmer, but it also helps to accomplish our objective of emphasizing your face...
which is the most important part of any portrait.
Tip #5 - Relax!  You can have all the right elements in place to have a great portrait session and have a less than desirable session because you are tense!  Relax.
  Breathe.
  A relaxed family is a happy family and produces a stunning portrait! Tip #6 - Color coordination is even more important for a group portrait.
 For example, if your group has eight people in it and just one person's clothes are not colored coordinated, it will (not might) ruin your portrait.
  Picture in your mind eight people, seven are dressed in beige khaki pants and navy polo shirts.
  The eight person (a woman for this example) has decided to wear a bright red dress.
  Can you see why this would ruin the portrait?  Now, the only exception to this is bridal portraits.
  But for now, we are talking about family portraits.
  It is very important that you take your photographer's suggestions to heart and make sure that everyone in your group is color coordinated.
You'll thank them later.
Tip #7 - If you are having your portrait taken outside at or near your home, choose an outdoor location carefully.
 The benches, the fountains, the lattices with roses and other pretty flowers climbing all over...
but keep in mind that what looks good to the eye might not look good in your portrait.
 For example, that beautiful lattice with the pretty flowers on it will make your portrait look very busy.
 The lattice and the flowers will be a distraction to you and your family.
  Remember, the most important part of any portrait is the face.
 So, you will want to keep the distractions in the background to a minimum.
 When looking for a location for your portrait, scope out areas that will enhance your portrait.
 Your photographer should be able to assist you in choosing a great location.
  Tip #8 - Listen to your photographer.
  In order to make the most out of your portrait session, it is crucial that you listen and follow the advice of whoever your photographer is.
  If you go to your doctor and he tells you to do 'X' and you don't...
do you blame the doctor or do you take responsibility? Why do I bring this up? Because it is one of the biggest pet peeves photographers have.
 It is suggested that you dress in a certain way based on the look you want for your portrait and then when you arrive for your portrait session, you are dressed totally opposite of the way that was suggested.
  It is the photographer's job to make you look awesome! I think an example would be good here.
  f the photographer suggest your family to wear all blue jeans and navy polos, it would not be wise to show up for your session all wearing different bottoms (some shorts - different colors, some jeans - some blue others red) and different tops (some tee shirts - different colors, some polos - different colors).
  Get the idea?  Contrary to popular opinion, photographers can't fix everything in the computer.
Tip #9 - Have fun!  Having your portrait taken is not like having a root canal (though you might think so!).
  If you click with your photographer, your session should be a barrel of laughs.
  There should be a light, fun atmosphere (if not, you might want to consider either rescheduling or finding another photographer).
  When everyone (you and the photographer) are having fun, the best portraits happen.