My main piece of advice is never open the filter without quick disconnects closed. Learned that the first day, flooded my room. I never open my filter under the stand for that matter, move it to where it can spill. Also, always use the disconnects when removing the filter so you maintain a siphon. Lastly, I like to fill my filter up with water (declorate first) so it primes more easily, and air leaves more quickly.
As for maintenance, depending on your bioload, you may not be cleaning much at all. You may or may not see a reduced amount of flow over the first 2 weeks to a month. It just depends on your bioload. Nothing to worry about. Now, you will get steady flow for awhile after that. Once it slows, again, that's when I tend to clean mine. On some tanks, it may be more than a year for me. Actually, it's often over a year as i don't stock my tanks heavily. I actually have been pulling my filter for cleaning at about a year, just to find out it's not dirty. So now I just wait until the flow is reduced. It all depends on your bio load.
I only clean my mechanical filtration (pads). I don't even touch my biomedia. I use to rinse it in tank water but I don't really see the benefit now that I stopped doing it. Even though you will see stuff in the filter, it's really not going to do much to rinse it. It is perfectly fine to do so, just do it in tank water.
I will brush out the impeller and that general area once a year or so, whenever I clean. If I had a high bio load where I had to clean ever 3-6 months, I would still probably only do it about every 3 cleanings.
Lastly, I tend to reduce the amount of mechanical filtration and add bio-filtration instead over time. So, lets say my filter has 3 pads. I do 3 pads for about 3 months, then take one out, adding bio media in it's place. 3-6 months later, take another one out. It may clog quick so if it does, I put it back. If it doesn't, I stay with one for the rest of the life of that tank. This is a technique some of us use but many do not.
Remember, everyone does things differently. I have found the way I have outlined gives me the best trade off of long maintenance intervals, quick cleaning, and good flow. Some people clean much more often to be at the peak of their flow, I just buy a bigger filter so I don't have to. Once a year cleaning that takes 15 min or less is great for me. Other people tend to do more than I do, nothing wrong with that.