If the walls are not smooth, there could be a lot of things wrong.

General

General things still apply, see maintenance webpage.

• Level your bed
• do z-offset
• do your e-steps
• use the temp-, flow- and retraction-towers
• PID tune your printer for bed and nozzle

Mechanics

Check if belts are tight. Do not overtighten them, but make sure they are not too loose. Is the carriage of the hotend wobbly? Then check excentric nut behind it. Make sure to tighten it, but you should be able to move a wheel with your finger by applying some pressure.
Clean rods of Z-axis and lubricate them with something like superlube of dry PTFE spray.

Clogs

Check your hotend for possible partial clogs or if you have a detoratiated bowden tube.

Flowrate

Check if your flowrate is not too high. Try to lower it a few percentages.

Extruder

Check tension the extruder puts on the filament.