To be honest, this card is quite useless in most decks. Let's look at the ways you can play with Plan B.

1-Install, Advance, Here, you're hoping the runner will leave it alone, as there are no 1 cost agendas. You hope to double advance or triple advance on the next turn. The runner will strongly suspect this is some sort of trap or an awkwardly advanced 3-pointers since you do not score it. Most runners will check it when it has 1 token and not touch it if it's sitting with 3 or 4 tokens.

2-Install, Advance, Advance Runners might be tempted to run an under-protected or naked double advanced asset, but most often than not, they will assume it's a trap and leave it alone. If you then pump it to 3, 4 or 5, you will arouse even more suspicion. The bait will not work.

3-Mushin No Shin + Back Channels It's a viable option, but it involves a four card combo (Plan B, the 3/1 or 3/2 agenda, Mushin and Back Channels if they don't run it). In a Jinteki: Personal Evolution deck it could find it's place.

4-Plan B + Trick of light Again, why don't you play Junebug or some other trap like Cerebral Overwriter instead?

5-The Ultimate Bluff You're Weyland and you're pretending to pull off a Government Takeover. You have a three-pointers or a Vanity Project in hand a Back Channels if they don't take the bait at 6 advancements. NOW we're talking!

An Offer only works on centrals, so that isn't an option. Would make a fun GT attempt though... —
Or you use Mushin no shin on it and score something out of hand if they check it, and if they dont, you Back Channels yourself to have money for the rest of the game. —

Darwin is a cute little program that does very well in a few niche Anarch decks that rely on a heavy virus suite. To make Darwin effective, you have to combine him with Virus Breeding Ground and run 3 Cyberfeeders. His evolution then jumps in speed from crocodile to Pokemon. Take one free credit from Cyberfeeder, click to transfer another virus counters or two and he's suddenly a Strenght 2 or 3, threatening most Ice on the board. Darwin gets a lot of benefit from e3 Feedback Implants, as well as Hivemind and obviously Grimoire.

Run him in a virus deck with Noise: Hacker Extraordinaire or Quetzal: Free Spirit and you'll be amazed at how versatile and useful he can be when given the proper support to evolve. You might want to run a few Festers, though, as the Corp will purge you quite often.

It's worth adding #Surge to the list of Darwin's synergistic cards. After 1 turn, Darwin can be at Strength 3. In the first several turns of a game, this can be substantial; Darwin can combat most cheap ETR ice before the corp has its large ice (or the economy for large ice) in play. —
Link to [Surge](/en/card/02081) ( @PureFlight ) —
Nope that didn't work either... guess card links don't work in these comments yet... —
Hivemind deserves more than a casual mention here - in fact it's the main reason darwin is seeing play again. If you're unning any sort of hivemind engine (using progenitor, hivemind, and virus breeding ground to fuel powerful but otherwise hard to use viruses like chakana, deep thought, gorman drip, pheremones... etc. etc) Then Darwin is the breaker for you. since these builds tend to keep 3-5 or more counters on hivemind, even a click one darwin can be used to break just about any ICE. —
I've never liked trying to bulk Darwin up -- it's too fragile, expensive, and time-consuming. I think Darwin works best in a deck that's already using Datasuckers and Parasites to handle threats -- he's a great supplement in such a deck, and works without much investment in his strength. —
Is Cyberfeeder just for his breaking ability or can you actually use it to put counters on him? —
Yes, you can, because it is counting as "using icebreakers". —