I like places of worship because of the artwork. In Malaysia the mosques are almost always closed to any but their own people, but the other religions are very welcoming.
I pop into temples and churches whenever I walk past one that looks interesting but I love Hindu temples in particular because the art is extremely colourful.
This one here at the end of Petaling Street, a place famous for it's fake bags and other goods, is very popular with tourists.
Etiquette is easy.
You can wear anything you like but in general it's polite for Westerners to avoid plunging sleeveless tops and shorts.
I think this is not so much for propriety but to show that you take the temple as serious business. If you come in a Sari like the local ladies, showing off your cleavage and mid-riff is perfectly proper!
You leave your shoes at the door and pay a man some money to make sure they're still there when you are back.
You walk in, wash your feet (clean feet is a hugely symbolic thing in Hindu culture) and then walk about in bare feet. (I always hope that nobody has verrucas and walk on tiptoe. So far I've perfectly all right.)
You can take pictures although in general it's polite not to do it when people are praying.
Hindu temples are still very much a part of daily life for believers, so there's always something going on. Don't let that put you off. Visitors are generally very welcome.
In the few dozen temples I've popped into, I've found worshipers and priests take it as a compliment to be asked the history of the temple, the meaning of the various offerings, and the history of the gods featured there.
They're usually very informative, but watch out! You may end up staying for a vegetarian lunch, and making a dozen new friends.
If you do stay for lunch, you'll be told it's all free. Don't listen to protestations but ask to make a donation to the temple, or local orphanage or something. Temples support a lot of charities so contributions are always needed.