Step 1: Care for your hair
Long hair needs to be maintained in peak condition as damaged hair will look strangely and unkempt. Healthy hair is much easier to style and manipulate so you'll be making your like easier if you look after it. Use a separate shampoo and conditioner rather than a 2 in 1 so that your hair retains its moisture. Shampoo with every shower, but only condition once or twice a fortnight, ensuring to comb it through when you do. Men's hair creates a lot of its own natural oils so you don't want to over do it.
Step 2: Products
Ask your hairdresser what product if any is right for you. There is a huge range of waxes, gels, sprays, and pomades available, but long hair generally requires less than short hair.
Step 3: Reduce body
If your long locks are particularly thick and have a tendency to bouffant, then ask your hairdresser to cut some of the body out of them. This should make it easier to style.
If this still doesn't do the trick then try using a hydrating product and a dense conditioner. This will add weight, and reduce the volume further.
Step 4: Texturizing
Getting your hairdresser to texturize your hair will remove excess bulk, and allow greater movement. This suits straight or slightly wavy hair, and shows off a good cut. Rub your chosen product over your hands, and in between your fingers. Get your hands right in the roots and rake your fingers through, whilst squeezing the hair between your fingers. Continue this, pulling hair in any direction you like, until you've have sculpted your perfect look.
Step 5: Growing out
If you are growing out your hair, make sure you make regular trips to the salon to keep it in good condition and help you through the more awkward phases. Every six weeks or so should do to keep the back and sides tidy. If you know the eventual look you are going for, always use the same stylist so you can work together to tame your hair towards the style you desire.
Step 6: Slick back
Johnny Depp has worn this look to great effect, but it's not for the amateur and you can end up looking smarmy rather than cool. Avoid it at all costs if you have a round face or thinning, curly hair because it really won't suit you.
If you are confident you can pull it off then apply product to damp hair, and brush your hair back with a wide toothed comb, using extra pressure at the sides to push the hair close to the head. Gently run your fingers through to break up the comb marks, to provide a softer look.