I've played about 4 hours of the game today now that it's out in the US, and here's some info I've gleaned from playing that isn't obvious. At all. But should help folks get started.
1. Random Encounters are Based on Trainer Level
Like actual Pokémon games, to find an encounter you'll want to go searching for those blasts of leaves and grass, but note that if the Pokémon is too high level for you, nothing will appear. At Trainer Level 1, you're pretty much relegated to Pidgey and Rattata, and there's not actually that many out there. At least, not in Downtown Seattle. You'll more likely get to Level 3ish using mostly Pokéstops if you're in a dense urban core. The higher your Trainer level, the more varieties of Pokémon you will encounter.
If you see a Pokémon on your screen, get it inside your trainer's circle, and then tap it to engage.
2. Capture By Flicking Your Pokéball
Once in "combat", you actually capture the Pokémon by pressing the Pokéball at the bottom of the screen and flicking it towards the critter. I've found lining the creature up near the bottom of your screen helps with the capture. It's hard to judge because there's no real angle you can view to get a good notion of depth.
When you press and hold the pokéball, you'll see a coloured circle that slowly shrinks. The colour indicates the difficulty of the capture--green is easy, yellow is mid-level, red is difficult. Godspeed to those who are red/green colourblind. If you time your capture for when the circle is at its largest, you seem to get a "Nice!" capture bonus more often.
|Zubat in my room, the green concentric circle shrinks then reappears. Time your throw to start when the circle is at its largest|
3. Pokéstops Give You Stuff
Pokéstops, like portals in Ingress, are generally based on popular locations or pieces of art. A fancy manhole cover; a local park bench with a plaque; a church bell. Those sorts of things. They tend to be dense in urban areas, and apparently suburban areas they're few and far between, leaving you with few options except to purchase pokéballs and other items with cold hard cash.
For the uninitiated, Pokéstops look like blue squares from afar, and when you're close enough to interact with one, it unfurls into a pokéball shape.
|Blue squares are Pokéstops. The circle to the lower right if my character is a Pokéstop I can interact with.|
4. Capture Everything
Even if you already have a specific Pokémon, capturing more will net you more Trainer XP, more Stardust (for upgrading Pokémon), and more Candies (for upgrading and for evolving). If you have like 30 Zubat, keep the highest CP (Combat Point) version, and then Transfer (using the button at the very bottom of the Pokémon's status screen) the rest to Professor Willow. You'll get an extra Candy for each one you transfer.
5. Pokémon Availability is Location and Time of Day
The inner core of Seattle seems to have a lot of Poison types. Down by the beach/park on the piers I found more variety, including grass, fire, and flying types. Zubat started appearing after 7PM local time, and I didn't see a Ghastly until about 10 PM local time.
Basically, Pokémon have similar "habits" to real life animals in terms of when and where they are active.
|This Nidoran really wanted some Taco Bell.|