You should use a toothpick, previously buffed with a fine sandpaper like the image below. You can use other objects, but with the toothpick you can do it without turning off the phone because it isn't a electrical conductor and you can also sharpen the tip very easily.
You should clean the area paint in blue below:
After this you should give special attention to areas in microusb port marked in red below which is where bolts fits and attach the cable to the port. You should try to clean as much as possible the dust that has entrenched there.
In my case after 5 minutes of hard work this was the result:
I used the lamp on my bedside table for a better look inside the door. Those black things are dust that came out of there now do not have any slack in the port works at 100% and I can move the phone without any problem.
How to fix female conector by flipswitch5point
Tried this, didn't get any dust :/ but what when I was cleaning it I saw the two little holes in the female side of the port that the clips for the male end are supposed to latch in. Turns out my male end was suffering from... impotence? Lol. I took a needle and adjusted the clips on the cable and it holds fine now. Just posting this for anyone else who's suffering looseness not caused by dust.