Mulching is the recommended way to not only control weeds but retain precious moisture and protect root systems from extreme temperatures. There are many different types and ways to apply mulch. Some of them can be very costly. I've found a better way to control weeds naturally and inexpensively.
If you're putting in new plants, be sure to follow planting procedures like proper depth and spacing as well as watering the holes where your plants will go. For established garden areas, make sure to hoe or pull weeds more than two inches tall. Also be sure you have applied any compost and tilled it into the soil well. Level the ground and break up any large clods of soil.
Then it's time for the mulch. Commercial mulches can be costly. An inexpensive alternative is to recycle newspapers under a shallow layer of shredded bark. The newspapers are of course free, and you can feel good about recycling them. Shredded bark can be purchased in quantity from a sawmill for a very reasonable price.
First, wet the ground to be covered. Don't make a mud puddle, but be sure to soak it well. Then lay out the newspapers. You can use 1-2 sheets, overlapping them to keep them in place. Put rocks or some other heavy object down to hold them down temporarily. Once you have an area covered, wet it again to soak the newspapers. This will keep the paper from blowing away and you can pick up and move the rocks or weights to the next area. Repeat this procedure until the entire area is covered.
If you have existing plants, you can tear and fit the newspapers around them. Make sure they snug right up against the base of the plants to keep the weeds out.
Then apply the bark mulch. Since you've already put down a weed barrier (newspapers), you won't need nearly as much bark mulch as is usually called for. You need only apply enough to hide the newspapers. Commercial applications calling for mulch at a 2 inch depth will require one 2 cubic feet bag to cover 12 square feet. So it will take about half that if you use the newspapers under it.
Which kind and size of mulch to use will depend on your budget. The treated mulch will help repel insects, but is about twice the price of plain medium sized bark mulch at a commercial outlet. Sawmills produce bark as a by product and will cost even less.
Make sure the mulch is evenly spread. To keep your garden weeds down, reapply as needed in the fall or spring each year.
The newspapers will work as a weed barrier and are free compared to expensive weed cloth. They will also retain moisture in the soil and degrade naturally to improve the condition of the soil in your garden. The mulch will cover the newspapers giving your garden or flower beds an attractive look. They too will degrade into soil-enhancing nutrients. Mulching will also help protect roots from extreme temperatures, keeping the root system warm during cooler spring nights and cooler during the hot summer days.