Question: If I were wanting to drive i.e. industrial relays which require 24v from a Microchip PIC what would I need to look at in terms of a general transistor circuit (and it's pitfalls when driving such a component).

Answer: 
A very simple and integrated solution may be the [NUD3160](http://www.onsemi.com/PowerSolutions/product.do?id=NUD3160). Basically the same footprint as a discrete MOSFET or transistor but with inbuilt protection for both the input and output.
I recently did something very similar to this as a beginner, and found MOSFETS very useful. You need a 24V source from somewhere to switch your relay, which should be connected across the drain-source pins of the MOSFET. You apply a voltage to the Gate pin (using the pinout from your PIC), and this essentially switches the relay-driving circuit on.

I made the mistake of taking the gate-threshold voltage in the datasheets as the voltage required to fully turn it, so rather than worrying about this it's much easier to just get a logic-level MOSFET, such as the IRL520. You need to make sure that it's capable of switching 24V and whatever current your relay will draw.

You also need to connect a diode in parallel with the relay to prevent damage to the transistor when it switches.