Probably best to avoid wiring them in parallel. All it takes is a small difference in voltage and current will flow from one to the other.
That said, with most of the electronics out there you should be able to connect the Grounds together, and run the Positive on one PSU to your electronics, and the Positive on the second PSU to the Positive side of the heated bed. Leave the Negative side of the heated bed connected to your electronics, and make sure the Grounds are connected to the electronics as well. This way, you have one PSU for your electronics, and one just for the heated bed.
This will work if the electronics use N Channel FET's to switch the output of the heated bed, such as what RAMPS does (check the schematic to be sure).
If you're still not sure, tell us what sort of electronics you've got and I'll see if I can knock up a quick diagram on how to do it.
That said, with most of the electronics out there you should be able to connect the Grounds together, and run the Positive on one PSU to your electronics, and the Positive on the second PSU to the Positive side of the heated bed. Leave the Negative side of the heated bed connected to your electronics, and make sure the Grounds are connected to the electronics as well. This way, you have one PSU for your electronics, and one just for the heated bed.
This will work if the electronics use N Channel FET's to switch the output of the heated bed, such as what RAMPS does (check the schematic to be sure).
If you're still not sure, tell us what sort of electronics you've got and I'll see if I can knock up a quick diagram on how to do it.