Some common sense is a pre-requisite to breaking fuel lines open, even to change a fuel filter. If you are not sure then get yourself a workshop manual specific to your vehicle or leave the job to a qualified mechanic.
Fuel Injection Fuel Pressures: Due to the pressures involved, all fuel hoses must be fuel injection rated and use only Fuel Injection type clamps if the fuel lines use worm drive style clamps. Normal hose clamps will cut into the hose and could cause a potentially dangerous leak.
Removal of Fuel Hoses: Fuel is pressurized from 2Bar (30PSI) to 5Bar (75PSI) depending on the system and even higher if the fuel return line is blocked or the pressure regulator fails. Extreme caution is required when disconnecting the fuel lines. Every system holds residual pressure for quite some time after the engine is stopped. Most vehicles have a way of safely bleeding off the pressure. Please use this method before breaking into the fuel circuit.
Fuel and Hot Exhausts: DO NOT allow fuel to contact a hot exhaust pipe. It may or may not ignite but the vapours are a health hazard.
Ignition Sources: 
Live ignition or electrical components are very dangerous when they come into contact with fuel or the vapour. Clean any spills left on the engine or around the engine bay before attempting to re-start the engine. NO SMOKING while working around the engine.
Ignition Spark: Due to the high demands of modern engines, ignition system output voltage and amperage are getting very high. Do not test spark by holding the HT lead or coil pack in your hand, the bite will hurt and in some cases cause severe injury or possibly death if you have certain heart conditions and especially don't test for spark just after you have broken a fuel line unless the spill (if any) has been totally cleaned up.
If you feel you have the confidence and knowledge to tackle working with fuel injection and high energy ignition systems then knock yourself out. Remember these precautions and also remember that on late model EFI with catalytic converters that you must take extra precautions to not damage the catalist.