Cable connections need to be cleaned and tightened as battery problems are often caused by dirty and loose connections. Don’t forget to check the earth cable, this can be the last thing that is checked but the easiest to fix.
If the battery has removable caps it is best to check the water at least every 6 months and more often as the battery ages. Distilled water is best as all the impurities have been removed and there is nothing left that could contaminate your cells. Don’t over fill battery cells especially in warmer weather because the natural fluid expansion in hot weather can push excess electrolytes from the battery and will make an awful mess.
To prevent corrosion on the terminals ensure the terminals are clean and have a good connection, a covering of grease or a battery terminal protection spray will help. If you continue to have problems try felt washers and cover them with petroleum jelly or even a bead of silicon sealer around the base of the post. The corrosion is caused by acid creeping in between the case and the terminal post and also excessive gassing, batteries are getting better and we don’t see as much corrosion anymore.