Try the diagram below. When the button is closed, the transistor sees +12 volts. When the button is open, the grounded 10K resistor allows the transistor to see 0v. The capacitor is there for debouncing, otherwise you will get glitches when the button opens and closes.
The 10K resistor going into the base of the transistor is there to limit the current. The transistor's emitter is grounded. One terminal of the relay is connected to +12v, the other is connected to the transistor's collector. There is a diode across the relay's terminals which may look like its backward. This is intentional. When the relay is on and working normally, the diode is not. But as soon as the button is released and the transistor turned off, the relay tries to keep the current going, and could fry the transistor. The diode allows the current to cycle around and dissipate while protecting the transistor.
The transistor is a general purpose NPN. The value of the small capacitor isn't too important. You could use another diode part number too.
As for the IR remote, I'm not too sure about that.