Battery life is less than expected

Reducing screen brightness, volume levels, and number of applications running are all ways to reduce battery usage. Also, turning off notifications from apps like Facebook and Instagram can improve battery life.

If you are in an area with bad service reception, you may want to put the phone on airplane mode. The phone will attempt to boost signal to gain reception, and this can cause the battery life to drain quickly.

Make sure you are using the charger designed for the phone. Sometimes chargers that fit but are not designed for the specific phone have electronic defaults that can shorten the life of your batter. Use the correct charger.

Make sure the battery is connected correctly and that it is clean.

If the above methods fail, I recommend replacing the battery. See this guide on replacing the battery: Samsung Galaxy R Battery Replacement

You can purchase a new battery from SamsungParts.com, amazon.com, or ebay.