How to Build a Modeling Portfolio?

Find a professional photographer to take your photos. Run an Internet search. Look through your phone book. Phone up local agencies and ask them which photographers they use.
Call up or, even better, visit the photographers you have found. Ask them about things like pricing, format of the film/digital photos and how long you usually have to wait between the shoot and getting the photos. Also, ask to see a sample of the photographers work.
Hire a professional make-up artist. If you are lucky, the photographer will sort this out for you but remember to ask if the cost of the make-up artist is included in the fee or if you have to pay extra. If the photographer isn't providing one, search for one in the same way you searcher for your photographer.
Look through fashion magazines and clothes catalouges and find poses you like. Practice in front of a mirror.
Decide on a number of looks you want to do. Ideally, you should pick at least three and they should demonstrate a wide variety (so not all jeans and t-shirt shots!!). If you have a special skill, such as ballet, you may even want to consider taking some photos in your ballet outfit and even making a pose.
Keep your hair, skin and nails in good condition in the run up to the shoot. If you need a hair cut, get one.
Once you have decided what clothes to wear, make sure they are clean and put to one side for the shoot well in advance. Ideally, you should have decided upon your outfits and have them ready at least 5 days before the shoot.
48 hours before the shoot, call your photographer and make-up artist to make sure everything is still ok.
The day before the shoot, make sure you get a good night's sleep and stay away from alcohol.
The morning of the shoot, double check that your bag is packed and that you have money for travel fares and parking fees. Aim to arrive 10 minutes before you are due (and make sure that time has accounted for applying make-up!). Carry the photographer's number on you and give them a call if you realize you might be late.
Discuss what sort of looks you want to go for with the photographer. After this, you will probably have your make-up applied.