I was like you in the beginning too, reallyclueless. when my first male betta blew a bubblenest i thought some soap had gotten in the water! lol. and i never let soap go anywhere near my fish or supplies.....
Water changes will actually cause your betta to make bigger, thicker bubblenests. they are happiest in pristine water and will be more likely to make the nests. happy betta = bubblenests.
Do keep an eye out for sparse (only a few bubbles) nests that are distributed over the tanks surface though. this may mean that your fish is not well.
On another note, the bubblenest will tend to dissipate when you open the lid of your tank (always have a lid! bettas will jump!), since the humidity level drops when cooler air comes in contact with the air above the water. don't worry, your boy will get back to work after your done doing whatever it is you are doing in his tank - feeding, water change, etc.
I personally do a minimum 100% water change weekly on my biggest tank that is in use, which is 2 gal. my 1 gals get twice weekly changes, and my 1/2 gal gets at least 3 changes a week, if not more. you can never keep the water too clean. make sure you are using an appropriate water conditioner (i use "betta plus" bowl conditioner by nutrafin - one capful per 2 litres <rinse the cap after or you get crusties on it>). it's a little expensive, but i find it is a good quality and my finkids are not worse for wear for me using it.
When i change the water i scoop my fish into a BIG and WIDE glass (i use big beer mug reserved for this purpose...lol) from the kitchen cupboard (give it a rinse in lukewarm water first in case there is residual dish soap) and make sure there is at least 3 times the height of water in the glass for the height of the fish and make sure there is at least an inch or so of air space at the top. don't worry, your fish will get a little upset, but it is only for a max of ten to twenty minutes. put a lid on the cup! tuppeware lid i use. then dump the gravel, if u use it, into a plastic collander and rinse twice with warm water, shaking collander so all gravel gets rinsed - need to get the poop out of it. rinse tank (mine fit in the kitchen sink), rinse plants, if plastic/fabric (i don't have experience with live plants). put gravel and plants back into tank. i usually have a big jug handy to pour new water into tank (run tap so water is room temp, fill jug, pour kinda slowly into tank - you get less air bubbles clinging to inside of tank this way. fill tank, minusing the amount of water in the cup with the fish, then add appropriate amount of conditioner. i then swirl the water around with a disposable plastic straw so all conditioner is distributed throughout. some people add a touch of aquarium salt, i do, but this is a personal preference.
I also use a floating thermometer in all my tanks, so i know exactly what temp the old water is and exactly what temp the new water has to be. sometimes there may be a difference of a degree or two, but my fish don't seem to mind. If by chance you've made your new water too warm or too cold, you can change it out a little with cold/warm to get the right temp, just make sure any more water added has the water conditioner in it. typing this reminds me of a time when i had used the last of my water conditioner and the tank was too warm and i couldn't switch out any water due to lack of conditioner, so before my fish went back home i put bags of veggies from the freezer around the tank until the temp went down! spoiled fish, huh? lol.
once you have the water changed, temp right, conditioner in (swirled around to distribute), i always wait a bit (five minutes or so) just to let things settle down and then i pick up the fish cup, angle it over the tank, and let a bit of the new water into the cup slowly until the cup is full and horizontal to the surface of the water, halfway out of the water. by now the fish should realize that he is "home" and swim out of the cup. I don't like netting my fish unless it is absolutely necessary - netting = lots of stress.
Hope this helps. and if anybody is appalled at the way i do a water change, then please do not hassle me, let me know how to do it better.