When I first started I pulled hard, real hard. I was totally upset because the vapor production was weak along with the taste. Over time I learned for the best flavor, vapor and throat hit a longer slower drag is needed.
The real question you have to ask yourself is why your fish lipping. Are you trying to get my vapor, stronger throat hit or more for taste? If your are sucking hard to get more vapor there are several things you can do. like previously mentioned make sure the tank isn't clogged and restricting air flow. The next problem could be with your atomizer, if you have been using t for a long time the coil could be wearing out causing it not to het up as much. To fix this you can either step up the voltage on your battery (temporary fix) or replace the col for your aspire ( cost a few bucks). If you are sucking because your looking for a stronger throat hit you can adjust you pg/vg ratio in your juice (higher pg stronger throat hit) or adjust your nicotine level. Also a straight pull to the lungs can increase the throat hit; this type of pull can be down right harsh though when first starting out. If your looking for more flavor I have found that "swishing" the vape around your mouth letting roll over your tongue really lets you experience the full flavor.
Hope any of this helps. Congrats on the switch
Happy plumes