This is the most simplest thing you can do to help the environment.
When I was growing up in India, it was a common practice for everybody to use re-usable shopping bags - mostly made of cloth. It has now become common place everywhere for retailers to pack shopped goods in nice plastic shopping bags - the bags serve the purpose of advertising, establishing brand image and providing convenience to customers. Now everybody is used to "not using" re-usable shopping bags.
But remember the adage "OLD is GOLD"? Some old practices are rather golden. These days most retailers are promoting the use of re-usable shopping bags. Where I live, retailers are selling and trying to promote the use of re-usable shopping bags. The bags are cheap (about a dollar) and the one time investment will go a long way in helping reduce the amount of plastic filling the land-fills.
Other ways to reduce the use of plastic bags & re-use them:
1. If you are in the store and buying only one or two items - ask the cashier not to bag the item and hand carry it.
2. If you don't have your re-usable bag with you - ask for a paper bag if you absolutely need a bag.
3. I usually have a couple of extra plastic bags in my car. In case I forget my re-usable bag or my re-usable bag is full, I re-use the plastic bags in my car.
4. It is a common practice for many to re-use the plastic shopping bags as trash can liners.
Recycle used shopping bags:
Do not throw plastic shopping bags in the trash can. Most retailers now accept used plastic bags and recycle them. Check for your local options to recycle used plastic shopping bags.