The theory behind the various mini-acts we have discussed.
Also, here's some more general info on building an act:
Opener: These are often the most difficult tricks to find. You want something magical (or at least interactive) to happen within the first 1-2 minutes of the trick. This is not the time for long, drawn out exposition. While the opener should still be impressive and should establish your persona, it also -- in a sense -- must be the weakest trick in the act so it doesn't get in the way of the tricks that follow.
Middle Piece(s): These are the easiest tricks to find. You want to have some variety in terms of effect, plot, premise, presentation, themes, and just overall "vibes." For more casual situations, you'll want 1-3 middle pieces depending on how long the act is going to be. These tricks are also the easiest to swap out. Just remember that the final phase of each trick needs to be more impressive than the final phase of the trick that comes before it. If you're trying to figure out what makes a trick more or less "impossible," read (or reread) Darwin Ortiz's Strong Magic and Designing Miracles books.
Closer: This should (obviously) be the strongest effect in the act. If it's a multi-phase routine, the first phase doesn't have to be stronger than the final phase of the last middle piece. But the finale has to be incredibly strong. Shuffling a deck back into new deck order order, changing the color of all the cards, finding 10 different selected cards, signed card to impossible location, etc. tend to be ideal climaxes for a show that uses playing cards.
Other considerations:
Laypeople generally categorize tricks by prop and overall theme, not by the specific magical phenomenon taking place. The old adage about not including more than one type of "effect" in an act (e.g. only one transposition, only one restoration, etc.) is nonsense. Sure, you shouldn't have every single effect be a transposition, but a coin transposition in the second trick and a card transposition in the fourth trick will not feel repetitive to an audience.
The act should have some kind of theme to it, even if the theme is just strong, simply-presented card magic that highlights your personality and connects you to your audience. Keep in mind who you (purportedly) are "onstage" and what skills you (apparently) have. There should be some consistency to your persona and the abilities you possess.
You don't need to have an overarching story or a cosmically-justified reason for doing magic (although if you do have great stories to tell and compelling motivations for performing magic, that's great -- just try to avoid old tropes and clichés). Especially in casual scenarios, you can (and often should) just do strong magic tricks for people. And keep it short! Don't do 45 minutes of magic at the dinner table for friends. Early on, keep it in the 5-15 minute range, and maybe stretch to 20 minutes as you get more advanced (but that can sometimes be too much). Leave your audience wanting just one more trick.