If you are planning on scaling some peaks this summer, plan on progressing slowly up the mountain to avoid such symptoms as: nausea, headache, shortness of breath, and difficulty sleeping. Symptoms usually occur above 8,000 feet. It is best to take your time going up so your body can acclimate to the different altitudes.
Camp the first night around 3,000 to 6,000 feet and then again at 6,000 to 8,000. If you feel sick at all, that is a sign to get down - and I don't mean boogie. Nope! You need to move to a lower altitude. Avoiding caffeine and nicotine (I don't understand the desire to smoke, especially in nature) since they can exacerbate fluid loss and rapid heartbeat that occur naturally as you go up in altitude.