Mowing a lawn will, unfortunately, not get rid of clover, and it may even encourage it to flourish. Let your lawn grow to a healthy height of over 3 inches and then set your mower blades no lower than this level. Higher grass will cut out the light that clover loves and discourage it from spreading.

Poison oak is similar to poison ivy in that it's in the same family of plants. Poison oak is identifiable by its rounded-off leaves and hairy leaf texture. Tree-climbing varieties live primarily in western states while low-growing poison oak bushes occupy the eastern states. Treat poison oak like poison ivy to get rid of it permanently.

Mowing your grass regularly, especially if you’re mowing close to the ground, can help kill Johnsongrass. Frequent mowing helps limit the spread of Johnsongrass and can even deplete carbohydrate reserves in rhizomes over time. The more time you leave in between mowing, the more likely Johnsongrass is to regrow and take over your lawn. 

No, definitely not. Pulling weeds by hand is the single most effective way to remove them because you're eliminating the entire plant—roots and all—so it won’t have a chance to grow or spread. Setting time aside a few times per week to pull weeds can keep them at bay. If the number of weeds gets overwhelming, then you can resort to other methods.