My German is weak but I have had this type of problem. The "ie" vs. The "ei". Think of "die for ie" and "eins for ei". So now when you pronounce them weiter sounds like wider (a greater distance between things, just like futher). And wieder is the same wieder thats in Aufwiedersehn, which I take to mean, I'll see you (again) later.
@lucky101man Great way to remember these. I'm stuck with the way i thought of it at school: that you pronounce the second of the two letters, because "ei" sounds like "I" in English and "ie" sounds like "E" in English. I now realise this is completely daft because English vowels have so many sounds, but I'm stuck with it.