Religious services are generally conservative. Even in casual environments, short dresses, skirts, shorts, or showing too much skin is generally not recommended. It’s really not an appropriate place for excessive cleavage, beach shorts, flip flop sandals, etc. However, every religious establishment is different. Some expect your “Sunday’s finest,” whereas others may welcome jeans.
When in doubt, something cute and business casual is generally accepted. For women, pretty dresses and pencil skirts worn with heels and light jewelry are no fail options. Or, you can wear dress pants or khakis and a pretty sweater or top with flats or heels. Men should go for a nice pair of slacks or khaki pants with either a polo shirt or button up, or with a blazer. More formal or special holiday services may require a suit. When in doubt, ask the establishment directly or friends/neighbors who may also attend.
You may want to also bring along mints or a small bottle of water in your handbag as some services can be lengthy. Heels may not be ideal if a great deal of walking or standing is expected.