The 5v/3.3v issue

I've placed on order for a TAIJIUINO Due Pro Board with Programmer & 7" inch TFT LCD module 800x480 SSD1963 w/touchpad off ebay and I'm waiting for them to arrive. I'm looking at using them at the centre of a musical equipment control centre. The LCD runs at 3.3v as does the Due board.

What are people doing in relation to the voltage difference in circuits? Obviously if it's a straight output a resistor and transistor can up the signal to the 5v level and there are several ways of dropping a 5v to 3.3v but what is the considered best practice? What is the best method for INPUT, OUTPUT and IN/OUTPUT? Looking at what I'm doing with MEGAs at the moment most of the circuits can be simply adjusted with alternative value components but some can't.... What are people doing with analogue inputs?

As long as the signal is not bi-directional, you can use a CD4050 hex buffer chip. Use a supply voltage to power the chip equal to the output voltage max you need.