Whether you are organic gardening or regular gardening, a weed is a plant that is growing where it is not wanted, it can have strong and healthy growth, and is able to overgrow valued plants by overcrowding, thus depleting soil nutrients and moisture that would otherwise be available to preferred plants.
Removing weeds by manually pulling them from the ground is the most common form of organic gardening weed control. It's easy to do, doesn't pollute the environment with toxins, and is also cost effective because it's free.
Grab the plant close to the ground, encircling its leaves with the fingers of one hand. Take a small-bladed knife or sharp-edged hand trowel with your other hand and use it in the soil to slide under the roots of the weed to loosen them and help remove the plant from the soil. Use care to avoid disturbing the surrounding soil, mulch, or leaf litter to prevent bringing deeply buried weed seeds closer to the surface where they could sprout.
Boiling water will kill any plant growth it touches. It is very inexpensive and simple to use. It is superb for killing annual weeds and can control and/or kill perennial weeds. It is a popular non-toxic means for killing weeds growing in cracks and driveways.
"Will some plants still resprout?"
Some perennial plants with long taproots (such as dandelion) may resprout from the lower root area if it has not been scalded. In a lawn you can remove the top growth and dig a hole above the root, manually removing some of the root if possible. Pour the kettle water into the hole and it will seep down and kill whatever sections of the weed root it can reach. Refill the hole with soil and sow some grass seed right away so there is no bare spot where airborne weed seeds can take hold.
If a weed resprouts in a sidewalk crack or driveway repeat the boiling water treatment. Each time the weed resprouts the growth will be smaller and weaker and the most stubborn perennial weeds will eventually die, usually after two or three treatments.