In rifts one can have skills based on 1 to 98% sometimes higher. The object is to roll under the skill percentage and if you succeed in doing that you perform the skill successfully. This is simple and pretty streamlined. However not all actions requiring a skill roll are the same. For Instance we will take medical doctor. The skill required to Diagnose the flu should not be the same as the one to find a cure for a trans-dimensional virus. I have seen a lot of Game masters handle this different ways. Everything from doubling or halving skills to percentile modifications; Personally I prefer the percentile modification. I have a standard set that I use. By having a standard set I am more consistent and my players have a better feel for what is going on. I break down the difficulties as the following
Trivial: This is something that is very easy. Often this is not something that requires a roll, but due to circumstances you need to. Examples of this would be cleaning a wound (Medical Doctor), Changing a tire (Automotive Mechanic, or Basic Mechanic), Land a plane on a nice clear day (Pilot: Airplane), Cartwheel (gymnastics). So why make people roll? It is the situational modifiers. Cleaning a wound is easy unless you have no medical supplies. Changing a tire is easy unless one has no tools. Landing the plane is easy unless it’s on fire. Cartwheels are easy but if you are in front of a large audience failure (99 or 100) is pretty embarrassing.
Routine: This is the stuff we do every day. We are pretty competent, but it usually is not that hard. This might include things like driving to work, Cooking dinner (cooking), Fixing a engine (automotive Mechanics), Sneaking out of the house without your parents hearing (Prowl) Nothing very complicated but what where you do things that you always do every day.
Standard: This is the stuff that complicates life. This is the basic level assumed in the game. These are skills that go above and beyond the average. Examples of this would be; repairing battle damaged robot (robot mechanics), Identifying a new life form (biology), Writing a really interesting article (writing), Surgery on a gunshot wound (Medical Doctor)
Difficult: This is when you’re asked to do something above what you normally expect. Often it includes danger. Examples of this Repair a skycycle ™ that fell from the sky (Aircraft Mechanics), Add a new feature to your power armor (Robot Electronics or Mechanics), Sneak past guards in fairly open area (prowl), Open a custom designed lock (lock pick).
Amazing: Amazing are things of legends, well maybe not legends but certainly stuff that will be remembered by everyone who saw it. This is the stuff that when you get together with friends they say "remember when…" This is stuff they warn you about on television not to try this at home. Examples would be: disarming a nuclear weapon in record time (Demolitions Disposal). Doing a Back flip off the back of a ATV onto the back of another heading the other direction (Gymnastics), Removing the cortical bomb in the borgs head (MD in cybernetics), Flying your skycycle into the opening in a deaths head transport while both are moving. (Pilot: Aircraft)
Here are some of the conditional modifiers.
Improper tools –10
No tools -30
While in combat –30
Under the influence –10 to –30
Vehicle in distress –10 to –30
Poor weather –10 to –20