A mojo bag is a tool that pagans use to assist in spell work. The way a mojo bag is made depends on what your goal is with the bag. A good way that i start with to make a mojo bag is hand making the bag itself out of whatever color cloth corresponds to the goal you are trying to reach. ex: Say that I was looking for a job and wanted a lil help. I would start by making a bag out of green, yellow, or gold cloth. (green=money, yellow/gold=success)
Next try to look up the right herbs, crystals, amulets, or personal items that will help you reach your goals. ex: we will keep it simple for this example I will fill my money bag with dried ginger root, cinnamon, and pyrite (fools gold).
Now before you start on anything make sure you have your altar set up with the right candles and incense too. Purify all of your tools and ingredients by whatever methods you choose for cleansing. I run my tools through incense or sage smoke to purify. Some mojo bags use incantations others use meditation to charge them. Just look into whatever type you want to do for your personal mojo bags.
If you are not sure don't be afraid to ask questions its better to know what your doing before you get started. Hopefully this helped a little. Good luck to you on your path. Blessed Be!