One should use at least mosfets, opto-couplers or transistors to electrically protect the circuit from the programming circuit.
Why? However, if you are suggesting using the above components (that's a pretty authoratative statement), maybe you know something we don't, so share with us...

In the meantime, do a forum search... it's all been discussed before... and in some threads you'll even find some schematics... eg Post #14 on this thread...

http://www.picbasic.co.uk/forum/showthread.php?t=516

People give you suggestions here, things they use, things that work for them. You can do what works for them, you can take the idea and create something of your own, or you are free to do something completely different. But hey, let's not post a detailed specification and shoot people down when they don't meet it exactly!