Learn a little about the area you are visiting. Speak to people who have visited the place before and know what to expect. Use the internet: a simple search on your favorite search engine for “«birding location» trip report” will tell you a lot about the place and its biodiversity.
Also, understand what to expect in terms of species. In my experience, while birding in India, guides will only show you stuff that you ask for. Make sure you know enough to tell the guide what you are expecting to see. A simple search on flickr, 500px or any good image search engine for the location will give you photos of species you can expect. Make a checklist if you can’t remember them all.
Here’s a list of things to follow/carry when going birding
If you are into bird photography, there are a couple of other things you might want to carry on the field. Here’s my list: 1. A good camera with good zoom. A good semi pro camera with digital zoom should be good enough to start. DSLR’s allow for more creative options. 2. For the DSLR folk, buy/rent a nice wildlife lens. Most birds and animals will stay as far away from us humans as possible, and if you need shots of small birds, you will need the focal length. Anything upwards of 250mm to 300mm should be sufficient. You can rent from Tapps, Toehold among others if you are in the Bangalore area. 3. Carry extra batteries/battery grip and memory cards. And leave your camera bag in your vehicle if you are walking. 4. You might also want to look at buying/renting a monopod if you are shooting in canopied forests or in diffused sunlight. This looks like a sturdy enough monopod to start with. 5. If you are going to a dusty place, get a cover for your lens and camera.
This is a heavily written about topic and there are tons of articles you can look up on the web. Here are some articles you can start with.
Principles of birding ethics
Here’s another that I really liked: The ethics of nature photography and the ostracising of photographers
That’s it. Oh, and lastly, go along with a good group, that appreciates birdwatching, and you will find your birding experience to be even more rewarding.