To start with I'm expanding on the idea I had back in 2010. Back then, I wasn't planning to have specific skills - instead I imagined having players describe their background and then roll against that description using a simple d6 system modified by stat bonuses.
My new concept allows for way more customization of a character. I'm designing this system with Swords and Wizardry White Box in mind; however, I think you could drop this into any game that is lacking a skill system.
Each character class gets a certain number of skill points during character creation. Most classes will get 3-5 points (the thief class I'm thinking of will get way more points than the rest). I haven't decided the exact number of skill points to give out per class just yet. I'll be covering this in another post.
Big Old Skill List:
Str - Athletics (covers climbing, jumping, etc..), riding, body development
Dex - Stealth, Disguise/Deception (Dex/Chr, covers pickpocketing), * Mechanisms(Dex/Int), *Sailing(Dex/Wis)
Int - *Engineering, *Healing, *Lores (pick one - Alchemy, Art, Astronomy, gambling, heraldry, tactics, poisons, etc..), *Craft (pick one - Smith, armorer, boyer/Fletcher, brewer, butcher, mining, etc...)
Wis - Tracking, Natural Lore (Animal, Herbalism/Plant, Mineral, Survival, Weather)
Chr - Influence, Trade, Streetwise
Int - *Read Magic, *Analyze Item - both of these require a good explanation of why you would know them if you aren't a wizard!
Any skills with * mean that you can't attempt using this skill (defaulting to the stat bonus only) unless you have trained 1 slot in it. Feel free to add additional skills or let players make up their own.
Competency and Modifiers:
All skill attempts use a single d6 die roll, modified by the stat bonus and the training bonus. If the skill has two stats listed, take the average bonus and round to the next largest absolute value integer (round 0.5 to 1 and -0.5 to -1)
Each slot = +1 bonus
No slots = Untrained
1 slot = "skilled"
2 slots = "expert"
3 slots = "mastery"
For Swords and Wizardry, I'd cap skills to 3 slots until 10th level. Beyond that I'd let my players go to legendary skill prowess. For other game systems, the GM should judge how many slots are used. You could also vary the die used, want more variation, substitute a d8 (or d7) instead of a d6!
With this skill system, never give players bonuses due to environmental circumstances. Deal with bonuses and penalties in the target value, covered below.
The DM sets the difficultly of a task, including all environmental factors. Most DM's are familiar with this type of roll against target number system and include any applicable factors.
2-3 = easy (I wouldn't normally ask a player to roll)
4-5 = moderate
6-7 = hard
8-9 = very difficult task
10 = near impossible
11+ = more or less impossible
Sometimes you may set the difficulty of fully completing the task so high a player can't ever succeed, but if they roll well (maybe a 5-6 on the d6) you could give them a partial success?
Also, if the difficulty is moderate ( 4-5) and a player with a +4 bonus, rolls a 1 or 2 on the d6, you may want to rule that they succeed but with a complication?
Keep in mind this skill system is supposed to be quick and dirty, let them roll, use your judgement and let them know what happens. When letting players roll some skills, don't tell them what them what they are aiming for (just tell them "it looks pretty easy, you should be able to do this (difficulty 4)" or "wow, this might be the hardest challenge you've ever faced (difficulty 10)".
Or don't tell them anything, give them the evil GM smile and say, "just roll the die"...
***This is a rules system being developed as house rules for my own Swords and Wizardry White Box Game, the rules set developed by Matt Finch. You can download a free copy of the rules here, but if you like them you really should buy a copy to support Matt, he is a really cool dude.***