As you collect items that you want to sell in your garage sale, it is good to designate an area to put them. This allows you to see how much stuff you have to sell and might give you ideas on how to group items for sale. I usually have a spot in my basement that I use all year long to collect items I intend to sell. So I might group toys in one area, clothing items in another, household items in yet another and books and movies somewhere else. If you store items in boxes, then you can just throw items in the appropriate box as you add items throughout the year. This way, when you are ready to for your sale, everything is in one location and easy to locate.
I would suggest that if it makes sense and is possible, price items as you place them in your collection area. This will save you a lot of time down the road. Pricing can take a significant amount of time so by doing it over time, there will be less to do at the end. One downside to doing this is you may change your pricing scheme somewhere along the way and you may need to go reprice some items.
As you gather your items, think about how you will group your items. Do you want to sell certain movies as a set? Do you want to group like toys together in a bag? Do you want to price socks individually or group them by size and color to sell together? If you’re not sure about how you’ll do it, you may want to hold off pricing those items until you decide.