How do I get spies?!

Sorry for posting so much today, I just got BNW and am figuring out all the new mechanics. My biggest problem right now is figuring out how in the dickens to get spies, and any help would be appreciated! I am currently in the Renaissance era, but I still only have 1 spy for some reason. How do I get more?

When any civ get into the Renaissance era, all civs get one spy. Then you get an additional spy for each era after the Renaissance.

Edit: ... and England gets an additional spy.

Build the National Intelligence Agency, a National Wonder. Gives you 1 additional Spy and all of your spies get level up.

The punchline of all this is that you can't build extra spies. One spy per era, plus one extra Renaissance spy for England, and one extra spy if you build the NIA. That"s it. Scarcity of spies is what makes decisionmaking about where and how to use spies important.

Not that.. you have A LOT of decision.
Like 4.
1. Plant a Spy in your Capital/High Potential Cities to defend from other spies.
2. Plant a Spy in A City State to keep up influence
3. Plant a Spy in an rival city to steal Technologies
4. Plant a Diplomat in a Capital to control their votes.

Ahh ok thanks for the help. For some reason it just felt like I should have more, since I was so far into the Renaissance. And yeah I wish there were more spies involved... do you guys generally guard your cities or not?

If you are leading by the number of technologies - yes, preferably. What I like to do is to send the first spy to a civ that has more discovered technologies (or the second best if I am the leader) - not sure if it changes with difficulty levels, but on Prince there is a high chance your first attempt to steal the tech will be successful. Once the tech is stolen, if you are among the leaders by the number of techs, send the promoted spy back to the capital. In most cases the spy will make it in time and soon kill the enemy spy trying to steal your tech. Easy Special Agent.

I usually only stick spies in cities if I want to level them up (only killing an enemy spy on counter-intelligence and stealing techs causes spies to level up, aside from National Intelligence Agency). Stealing techs takes a long time; unless you have several spies doing it in several places, it's not going to change your tech position unless you have as much science output of your own as the civ you're spying on (and so are discovering new techs at the same rate as well as gaining them by spying) since by the time you've stolen a tech they've probably researched two.

This is why constabularies and police stations work the way they do - delaying tech steal makes it largely useless, even without a counterspy on defence. I only use a counterspy if I have a key tech others don't have that I think they may be able to steal (say, if I'm first to Acoustics and don't want to risk being beaten to Sistine Chapel, or first to Astronomy and don't want to be beaten to discovering all the other civs), or if I'm so close in tech to a nearby rival that stealing could put them in the lead.

As a disclaimer, though, I'm playing on Immortal where I'm never anywhere close to tech leader until the latest game stages anyway, so I don't have a lot to lose.

In general, though, I'd say that stealing techs is useful to level spies but most of the time (once they hit Special Agent) you'll want them stationed in city-states or as diplomats. Counterspying is the lowest priority of all unless you're being spied on a lot, and so have a good chance of levelling up a spy very quickly (if he catches multiple spies in quick succession). Also, you can't get intrigue from counterspies and that can be valuable (although you can get a better idea of who's spying on you, since you're more likely to identify the spy - if you kill them you always know who sent them).