Each Applet you enable on IFTTT has information on how often it runs. You can see often they run by visiting Manage Applets and selecting the Applet. You'll see some text near the bottom that states This Applet usually runs within [Time]. This is dynamically generated based on the past several times that Applet has run.
The frequency in which Applets run is largely dependent on the service(s) you're using. If an Applet isn't running as quickly as you expect it, we encourage you to check with the service owner. Most service owners have tools available to them to help them figure out if their IFTTT integration can run a bit faster.
To force an Applet to run, first select the Applet and then select the "Check now" button. We don't recommend this as the primary way to use IFTTT but it can be handy for troubleshooting. If it doesn't run, there may not have been any content for the trigger to activate since the last time the Applet ran. Try selecting "Check now" at a later time.