Learn the Dutch alphabet. Think back to the first thing you learned when picking up your native language: the ABCs. Each language has it's own alphabet and, though much of it is similar, the letter sounds can be different and you may find one or two letters more or less than in the English alphabet. The letters of the Dutch alphabet are A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, IJ and Z.
Take a Dutch language class. In order to write a language, you must also be able to speak it. During instruction, you will learn numbers, letters, spelling, grammar and vocabulary, among many other things.
Watch Dutch movies and television. Unlike most other countries, in Holland movies and television in other languages are subtitled instead of dubbed. This means that when the Dutch watch American television shows, they hear the actors in English and look to the bottom of the screen for translations. As a non-Dutch speaker, this enables you to do just the opposite. You learn typical Dutch phrases and slang, along with vocabulary and sentence structure. Sites like 2bdutch.com take this to the next level by taking television programs in Dutch and adding Dutch subtitles as well as subtitles in the language of your choice at the bottom of the screen. This allows you to see and hear what's being said in Dutch as well as the translation in your native language.
Get busy reading. The best way to learn how to write is to read. Start with Dutch children's books. Two examples include the adventures of the cute little bunny "Nijntje" and the fat orange tabby "Dikkie Dik." Then graduate to the brother and sister duo "Jip en Janneke" before moving on to check out more literary works like Harry Mulisch's "Twee Vrouwen". Publications like "Kids' Week" put news stories in kid-friendly language, making it easier for beginning to intermediate Dutch language learners to read.
Let the internet help you. There are tons of resources online that will help you learn to write the Dutch language. The site Verbix.com, for example, offers an online verb conjugator. Just enter a verb in its infinitive form, hit enter and wait for Verbix to do it's magic. Online dictionaries like InterGlot are also helpful, as are online translators such as Babel Fish.
Practice makes perfect. Write emails, letters, blogs, comments, notes and anything else you can think of in Dutch. Have your teacher or a native Dutch speaker proofread it for mistakes and ask them to offer suggestions. Find a Dutch penpal to write to. Use this as an opportunity to learn about the Netherlands and its people as well as honing your Dutch writing skills.