Derailleur Adjustment

Just changed rear derailleur on my roadie, having trouble getting the shifts in line with the chainrings, despite a few attempts at adjusting cable tension etc… Any tips or is it just a matter of trial and error?

Front shifting? Double or triple? Mostly trial and error. Eyeball the low limt screw on small ring and clamp cable on tight. Use barrel adjuster to tension good and solid. Shift to front, making sure high limit screw isnt stopping the range of movement.

Rear is easy: put it on the smallest cog, crank the cable tension, check shifting. Repeat as required.

yes as he said, and then also use this Park tool website for images.
Park Tool Website

They update pretty often I use it a lot- the site that is

all for rear derailleur adjustment…

put it in smallest cog, screw adjusters (on frame and at rear of derailleur) in fully, check cable tension, it should be twangy and taut but not tight… Adjust derailleur movement high screw, then shift to about 4th cog up (on a 9 or 10 speed system). Use the barrel adjuster to fine tune for perfection, and don’t forget to run up the cassette and check/set your low screw so the mech doesn’t shift into the spokes.

Run up and down, check the cable hasn’t slipped, then settle back in a comfy chair. You’re done