Make sure that you are holding your pipette vertically when pipetting. The more viscous the solution, the slower you should release the plunger (and you may want to leave the tip in the viscous liquid until you no longer see the volume increase). Beyond that, I would say make sure you are taking your time until you're comfortable pipetting and use a balance to check your accuracy by pipetting volumes of water and measuring the mass. 1 ml of water should weigh 1 g. Hope this helps!
