“What'd you do, just pick people randomly?”

You were talking with your friend about voting in the recent election. He said that when he voted, he didn't know anything about the candidates. You wonder how he decided who to vote for. You ask:

What'd you do, just pick people randomly?

What'd

When you're pronouncing "What did" in casual conversation, it's often shortened. This is written as "What'd" when you want to represent casual speech in writing. But in the sentence above, the words "What did you" can be pronounced "Wuhju" or "Whuhdid you".

just (do something)

You use this phrase when the action you're describing seems easy, simple, fast, or unimportant:

I just googled "new york florist" and that was the first shop that came up, so I called them.

I usually just fast forward through the commercials.

In the example at top, the speaker thinks that his friend voted without thinking carefully about it, so he describes it as "just" picking people randomly.

(do something) randomly

Doing something "randomly" means doing it without a plan or a reason. In the example above, "picking people randomly" means voting for candidates based on things like their names, their location on the ballot, and so on.

Some other examples of doing things "randomly" include:

I randomly decided to drive to the beach on Saturday.

Police aren't allowed to just go out and randomly search people's homes and vehicles. They have to have a warrant.