Mosquitoes. They've been around for around 100 million years. And for 100 million years they've bred and diversified into 3,000 species - all different. In North America alone there are over 170 different species. Worldwide mosquito-born diseases are responsible for the death of more people than any other single factor. Mosquitoes in North America carry the risk of encephalitis for people and heart worm for cats and dogs. Though their vampiric tendencies may seem purely sadistic, mosquitoes don't subsist on blood-lust; the blood is important in necessitating the development of the eggs in female mosquitoes; the bite simply feeds the cycle of propagation. So those red bumps on your skin have borne more than your irritation.
So you don't want mosquitoes. If you're really itching to know, the best strategy against their spread is to completely stop them at the source. Mosquito breeding grounds around your home or neighborhood are often obvious; look for stagnant water. Water is often found stagnating in old tires (e.g. tire swings,) buckets, bird baths, swimming pool covers, barrels, flower pot saucers, wading pools, clogged gutters, drainage ditches, eavestrough, &c. High grass and weedy, overgrown areas are also mosquito havens; adult mosquitoes are most active in the evening and spend the day awaiting the night, protected in foliage. Mosquitoes tend to stay within one mile or so of their breeding ground, so if you live in a rural area there might be a lot of ground to cover. Considering that one female mosquito is capable of laying 100 to 300 eggs at a time, producing somewhere between 1,000 to 3,000 offspring during a lifespan, against all efforts to stop them, mosquitoes might persist and abound beyond your ultimate control.
What you can do at the very least is limit their attraction to you. Mosquitoes find perfumes, perfumed soaps, floral fragrances (lingering perhaps from fabric softeners or dryer sheets,) hair products, scented sunscreens, cosmetics and deodorant to be seductive. Inversely, when you work out you sweat, you smell and you increase your output of carbon dioxide and lactic acid. Though you probably don't find your BO attractive, mosquitoes do and any mosquito (within 100 feet / 30 meters) will find you. Try to avoid wearing dark clothing if you can. Mosquitoes have very poor vision and you only help to accentuate yourself as a target if you resemble a large, dark and nebulous mass of foliage or water. In addition, long sleeves and pants - anything that decreases vulnerable surface area - will armor your skin against even the most indefatigable of mosquitoes. Keep mosquitoes outside by making sure that the screened windows and doors of your home are properly secured and completely sealed of 'leaks'.
Becoming unattractive to mosquitoes doesn't neutralize you as a target, however. A mosquito's attraction to you is quite natural, so it's sensible that you should attempt to detract mosquitoes naturally. Mosquitoes hate garlic. Take garlic supplements, make a meal out of it or rub a garlic clove on your exposed skin, crushing it first because it's the juice you're applying. Simple oils rubbed directly on the skin or clothing will be fragrant and won't have the nauseating effects of an anti-mosquito chemical vapor (which smells awful, from what I remember.) Try: lemon eucalyptus oil, cinnamon oil, citronella oil, rosemary oil, lemongrass oil, cedar oil, peppermint oil, geranium oil, Castor Oil or clove oil. Try mixing real vanilla half-and-half with water or crushing Pennyroyal and mint together, then carrying it with you wrapped up (say in a bandanna.) Other simple around the home applications and remedies include: Vicks® VapoRub®, Avon® Skin-So-Soft® bath oil and vitamin B-1 tablets (Thiamine Hydrochloride 100 mg.)
In the Garden, there are natural remedies to be planted. And there are so many to choose from: rosemary, marigolds, citronella, Horse Mint, basil, lemongrass, catnip, garlic, tansies, lemon oil of eucalyptus and Mosquito Plant (there are two types.) These plants and herbs are highly effective mosquito repellent agents. They can be grown and clipped and ornamented around the home, shown off in a vase or carried on your person to ward off blood-suckers.
If you so choose, there are alternatives to home-grown techniques, several in fact, each ranging in expense and approach and all of which are supposedly effective and certainly divisive anti-mosquito devices to try. However, consider the following as a disclosure: Special candles made of beeswax and citronella (an essential oil extracted from a citrus plant of the same name) produce smoke when burned that repels mosquitoes. The obvious drawback: a smoke tail is limited to a single coil and subject to changes and diffusion in wind conditions. The smoking coil is also a source of CO2 which is a mosquito attractor (prey mammals expel CO2 naturally.) There are machines which attract mosquitoes and then suck mosquitoes into the machine as a trap by process of a fan or ZAP the insects electrically (so that they die via explosion; the remains afterward are subject to the wind.) The machines, however, are full of bugs; research shows the machines aforementioned (bug zappers) actually attract and kill approximately 3,000 beneficial insects in one night - a figure paled in comparison to what might be a handful perhaps of mosquitoes killed in the same span of time. Also, the UV light emitted from a bug zapper polarizes when it reflects on the surface of water. Mosquitoes follow this polarized light to breeding eventual grounds. Lastly, due to a lack of conclusive evidence, there is a tremendous amount of skepticism over the effectiveness of machines thought to repel mosquitoes sonically.