The Praxis writing test closes with a pair of essays, and you have half an hour to write each one. The first is an open response in which you're asked to present your position on an issue. The second is a source-based essay that is graded more on how efficiently and clearly you incorporate and cite source materials. Keep these tips in mind:
Don't spend a lot of time making an outline before you start writing either one of the essays. Length is not the be-all and end-all, but it does matter, so you want to be writing for the vast majority of the allotted time. How eloquent you are and how clearly you seem to understand the issue matters a lot more than whether your points are in some kind of strict logical order, so don't stress out about micromanaging the organization of your essays.
Your open-response essay should clearly state a position somewhere near the beginning, but you don't have to state an uncompromising thesis that won't leave you any room for admitting when the other side has a good point. On the contrary, making it clear that you can understand why the people on the other side of the issue may see things differently is a sign of philosophical maturity that improves your score.
Don't try to use a bunch of big words for no reason. They make your essay annoying to read and don't help your score. The trick is to seem like you enjoy writing, not simply to deploy a bunch of big words that you memorized for the test.
On the source-based essay, be sure to quote from all the authors included in the sources and to use proper citation format after the quotes (the author's last name followed by a comma and the year of publication if you're using APA style, or the author's last name followed by the page number the quotation is from if you're using MLA style).
Sometimes the passages on which the source-based essay is based include "quotes within quotes" — asking you to cite authors who are themselves citing other authors — to try to trip you up. So be sure to keep straight whose ideas are whose.