The first step to creating a great portrait is to get great reference images. Now sometimes you don't have a choice of reference if you are working with a client with a specific image in mind. If you are taking your own, here are some tips that will help you get the best results!
Keep your camera at eye level- You can break this rule of course, like all of these rules, but you should have a specific purpose for doing so. Typical portraiture is seen from eye level of the subject.
Keeping the shoulders in mind: Pushed back is more defiant and manly. A shoulder close to the face is coy and feminine.
Lighting- The mood of your piece can change depending on the lighting you photograph your subject in. Dark and brooding? Use artificial light sources or perhaps a backlit subject. Cheerful and Innocent? Sunny natural light will give you the best results. Although it's simple never underestimate the drama you can create with a single lamp shining on one side of the face.
Color- Keep your color palette in mind when you are creating your portrait. Using pastels will give a much different feel than neons. Think about the person you are representing. Are they outdoorsy? Use earth colors for a natural adventurous look or maybe they'd prefer a simple black and white with all the drama.
Proportion- When drawing the face the key to capturing a likeness is proportion. You should keep these three relationships in mind when you start your next portrait.
- Width and Length- Ideally there should be 1 eye length between the eyes and 1/2 of an eye length on either side of the eyes. You should also measure from the top of the skull to the chin to give you the correctly sized face structure.
- Eyes to Nose- The triangle created from the outside corner of the eyes to the end of the nose varies significantly from person to person so pay special attention to this proportion when trying to capture a likeness.
- Eyes to Chin- This will create a space between the nose and the chin where the mouth will sit. Getting this space proportionally correct will is vital.