Okay, this might belong in the general dominion section, but I think it's pretty useful to think about these when designing cards, whether you want to follow them or not.
Number 4: +2 Cards +1 Action. Laboratory is the simplest version of this card, but many other cards, such as Advisor, Warehouse, and Hunting Party fit into it as well. Most cards based on this have good self-synergy and can cost a lot. The effect has a cost of $5, as Laboratory shows.
Number 3: +$2, +1 Buy. Again, woodcutter is the simplest form of this, but other cards like Nomad Camp, Bridge, Merchant Guild, and even Festival can fit in. It's worth $3.
Number 2: +1 Card, +1 Action, +$1. This is the only of the top 4 without something exactly it. There are surprisingly many versions of this card, including Market, Peddler, Highway, Baker, Tournament, Treasury, Grand Market and probably more that I forgot.
Number 1: +1 Card, +2 Actions. This is by far the most common of the archetypes, even having a name all to itself for the effect. Versions of it include Village, Mining Village, Worker's Village, Fishing Village, Native Village, Border Village, Bazaar, City, Farming Village, Bandit Camp, Fortress, Wandering Minstrel, Plaza, Hamlet, Shanty Town, and Walled Village. That's 16 cards that do almost the same thing! I guess they are so common because the effect is useful and enjoyable to have in many different types of games.
Okay, looking back at the 4 archtypes, each of them is primarily responsible for one of the vanilla actions. Only the +Buy one does not have the cantrip effect, and that is because in order to use buys well, you need to have money to buy things with. That is why it has money, I believe. Number 2, the money cantrip, is interesting because its worth is somewhere between 4 and 5, and so it cannot be priced as a normal card. I think number 2 is probably the archetype most open for new cards in, because its position allows complications to bring it to a whole number, and because there is not vanilla card for it, it cannot be strictly better than another card.
Whether you want to create wholly new cards or to stick to something tried-and-true, it's important to know the common archetypes either to create new versions of them, or to make sure your card does not fall into any of them.
