Do you have any previous foreign language training? High school Latin, etc?
I took the DLAB in '86 - it hasn't changed, to my knowledge. I graduated from DLI in 1987. I was cadre there '02-'05. I speak English, Spanish, some Turkish, some Russian, and a little Arabic (MSA). I'm not bragging, just trying to give you my bona fides before I give you advice.
The DLAB is about your ability to learn basic language
skills. It's about grammar and syntax (sentence structure) - and a little vocabulary. In a very short time, they give you rules and vocab and then see how well you picked up the rules - but you know how the test is structured
The best way you can prepare for the DLAB is to review basic English grammar skills.
Basic grammar skills.
Basic grammar skills......have I made my point? The whole point of the test is to see if you have the aptitude to learn quickly and turn it around.
I say this because 1) I know, 2) becasue, when possible, at DLI, each student goes through a headstart class before actually starting class - guess what? Basic English grammar. 3) the method of instruction there is "stick a fire hose in your mouth...."