Of course, this seems like a no-brainer. I recommend shampooing your hair in the morning, but don't shampoo again. Many guys make the mistake of shampooing too often which can cause your scalp to actually produce more oil. When shampooing, select a professional product specifically labeled for oily hair -- look for shampoos containing tea tree oil or menthol. I've also known guys to use a touch of dishwashing liquid to help fight oily hair and scalp.
I've known people who have had good success reducing oil by using a natural rinse of lemon juice or vinegar. Simply mix the juice of about two lemons with a quart of distilled water or about two tablespoons of white vinegar with a cup of water. Rinse your hair thoroughly with either mixture which should be gentle enough for your hair and still act as an astringent to remove excess oil. Avoid getting too much of the mixture on your scalp and rinse with warm water afterward to remove any lemon or vinegar residue.
Examine Your Scalp
Is your scalp dry? Ironically, a dry scalp can produce more oil which then gets in the hair. If your scalp is dry, use a shampoo for dry scalp.
Brushing the hair frequently can cause the scalp to produce more oil, so use a wide tooth comb (or fingers) when possible to style your hair and then leave it alone.
Skip Conditioner and Products
Using a conditioner will often make your hair appear even more oily, so if yo have oily hair skip the conditioner altogether. Hair products that contain shine elements will also make your hair look oily. I recommend using a matte finish paste (sparingly!) to help reduce an oily appearance. Using one (or all) of these suggestions should help reduce the greasy appearance and give your hair a healthier appearance.