This tutorial demonstrates how to use the search feature. After looking over this tutorial you should be able to execute powerful searches and find PBBGs that match very specific criteria.
This tutorial is slightly out-of-date, but should still help to explain the search feature.
When you visit the search page you will see the following:

The default query has one condition -- the search results will contain all games that have a title entered. Since game title is a required property, this will list all games in the directory. You can also see that the results will be sorted randomly. In order to run the search and view the results, click "execute search". This will display all of the games in the database sorted randomly.
Of course, you will want to customize your query. To do so, start by clicking on the word "Title". You will be presented with a list of properties that you can specify restrictions on.

You can start by placing a genre restriction by clicking "categorization: genres". You will then see the following:

If you were to execute the query above you would see all games that have at least one genre specified. Let's keep going -- click on the "exist" text.

Then click on "include".

Now you can choose which genre you will require. The default is action, but only because it's at the top of the alphabetized list. Click on the word "action" to change the genre.

Clicking on "strategy" yields the following:

If you click "execute search" at this point the search feature will return all games that belong to the strategy genre, and the results will be sorted randomly. This is where things get interesting. Click on add condition (at the bottom left) and you will see the following:

As you can see, your query now has two conditions. As before, the "title must exist" condition doesn't actually restrict anything, so I will change the second condition. With a few clicks, similar to the procedure followed above, you can set up the following search query:

This query says that I want to search for all warfare-themed strategy games. You can keep adding conditions in this manner. For example, maybe you only want to return games with 2D overhead graphics that were launched prior to 2005. You probably also hate popup ads, so you can omit games with popups from your search results. Now you have the following:

Now you can choose your sorting option. By clicking on the word "random" you will see a list of sorting options, similar to the following:

Suppose you want to return games by the amount of traffic they receive -- you can do this by sorting by Alexa Traffic Rank.

A lower Alexa Traffic Rank indicates more traffic, so you probably want to sort listings from low to high. To do this you can click on click on "high to low"...

...and change it to "low to high".

Now the most heavily-trafficked games will be shown first in the search results, provided they meet all of your search conditions.
To run the search and view the results click on "execute search". That's all there is too it!
A few things to remember:
-You can have a maximum of five conditions per search.
-Games will only appear in the search results if they satisfy all of your conditions.
-If you choose a sorting property, then only games with that property in place will show up in your results. This is important -- the sorting option effectively narrows your search. For example, if you sort results by "round length", then only listings with the "round length" property entered will appear in the results.
Happy searching!