The "generic" way is to

Figure out the maximum "length" of the timers (use Mr. E's Multi-Calc).
Pick an appropriate timer and prescaler.
Figure out what the pre-load count should be for the time interval you need based on the timer, prescaler and oscillator.

The counter will increment from the pre-load value and when it reaches maximum count (0xFFFF for a 16 bit counter), it will set the timer's overflow flag bit (INTCON.2 in the case of TMR0).

So to intialize:

Load the counter with the pre-load count
clear the timer overflow flag bit
enable the timer

Then --

Code:
Top_Of_Main_program:

do some stuff here

IF INTCON.2 THEN              ; the bit is set, so overflow has occurred.
    TMR0H = HighByte of preload value
    TMR0L = LowByte of preload value    ; the order is important!
    INTCON.2 = 0                                ; Clear the flag bit
    ;Do what you want here when the timeout value is reached.
ENDIF


Goto Top_Of_Main_program