Summarize:

There are a number of symptoms, referred to as pre-syncope, that you may experience immediately before fainting. Most fainting spells occur when you are standing, and recognizing warning signs will help you prepare yourself if you do indeed faint. In addition, awareness can also help to prevent a fainting episode and will help you stay safe if you do faint. Common symptoms include yawning, a sudden sweat, nausea (sickness), fast and deep breathing, confusion, lightheadedness, blurred vision or spots in front of your eyes, and ringing in your ears. The symptoms of fainting can come on very quickly and with little warning. If you experience the above symptoms it is a good idea to conduct 'antigravity' measures, which when done immediately upon feeling symptoms, can help you avoid a fainting episode.  Medical experts suggest that you lie or sit down and place your head between your knees. These positions will help restore blood flow to the brain and can prevent a fainting episode.   If standing, you can also cross your legs and tightening your abdominal muscles. This is effective if you are in a crowded place and you are unable to lie down immediately. By preparing, you can ensure that you are in a safe and secure place when you faint. Try telling someone near you what is happening and ask for assistance, try lying down, or try bracing yourself against a wall to prepare. If you find yourself on stairs or other precarious surroundings, sit down and hold on to a railing immediately. If you do faint, blood flow will resume to your brain naturally and you should regain consciousness in two minutes or less. It is normal to feel weak and confused for 20 to 30 minutes after fainting. Remain calm when you regain consciousness. Also, take some time to lay on your back to allow blood flow back to the brain. You should also hydrate yourself with water.
Determine if a fainting spell is approaching. React quickly to the symptoms. Prepare yourself for losing consciousness. Take it slowly if you do faint.