1. You can use Pages, Word, Keynote, PowerPoint or any third party drawing app. I recommend one with a free-shape polygon tool (click to make a point, drag to make a line, click to make another point, drag to make another line, etc.) I use Intaglio for the Mac. It's not free, but it has much of the same functionality as the long lost MacDraw, so it's great for counter design and layout.
2. Use the Ruler or Dimension functions to create a grid equal to your counter size. Draw squares, lines or whatever counter shape you want and then duplicate the shape along this grid.
3. Google images for any graphic elements. If you want to create silhouettes, just use the free-shape polygon tool to build a silouhette around the image.
4. Scale image evenly to fit inside counter.
5. Use text tool to create text boxes for any numbers, words, or what have ye pertinent to the counter.
6. Once you've filled all the counters, print to a cardstock (NOT regular paper).
7. Using spray adhesive or glue stick (NEVER "wet" glue or paste) to affix the counter to sheets of poster board; makes the poster board larger than the counter sheet, and you won't have to worry about alignment issues.
8. Trim. Good quality office scissors will work fine; you don't really need a craft razor. However, I don't recommend a paper cutter, as these seldom cut straight, but tend to skew the line at an angle to your intended cut.
9. If you want two-sided counters,do cardstock to cardstock (careful with the alignment) or accept that you will have thin counters and just print front and back on the heaviest cardstock your printer will accept.