How do I know if I am dehydrated? Dark urine, urine with strong odor, not having to urinate, fast heart rate, muscles stay excessively sore.
How much should I urinate daily? At least 4x/day (~8-10 fl oz each time).
Which electrolytes do I lose during exercise? Sodium, Chloride, Potassium.
How should I replace these electrolytes? Likely you already consume enough sodium chloride (salt). Potassium can be replaced through bran cereal, meat, fish, milk, yogurt, broccoli, raw carrots, legumes, avocados, bananas, citrus fruit, potatoes and nuts (among others).
Should I drink water during or after exercise? Drink it before, during and afterward. It is best to be hydrated throughout your workout because you lose so much fluid through sweating. You need to drink even if you do not feel thirsty.
Is it better to drink a large amount at once or small sips? It is ideal to drink a larger amount at one time (~8 fl oz) because it will pass through the stomach quickly. Try to do this every 15-20 minutes.
Do I need sports drinks when exercising? Water is sufficient during usual workouts (30-60 minutes). But if you will be exercising or playing a sport for several hours (especially outdoors), a sports drink can help to replace electrolytes and a little sugar.
Baechle, Thomas R, Earle, Roger W (editors). Essentials of Strength Training and Conditioning, 2nd ed. Human Kinetics. 2000. Pages 246-249 (Ch 12: Reimers, Kristin & Ruud, Jaime. Nutritional Factors in Health and Performance).