Anything else
Most of what I am asked for is reptiles and amphibians. But the question I like best is the odd one: someone who wants butterflies, or spiders, or orchids, or who just wants a forest explained properly without a taxon attached.
General natural history
A trip with no particular target, built to show you a place and not a list. Lowland forest, cloud forest, a wetland, a night walk, and someone to tell you what you are looking at and why it is there.
This is often the right answer for a group with mixed interests, or for a first trip to the tropics where you do not yet know what will grip you. In my experience it usually turns out to be something nobody predicted.
Something specific
Butterflies and moths. Spiders and other arachnids. Orchids and epiphytes. Stick insects. Bats. Fungi. Freshwater fish in forest streams. Whatever it is, the method is the same: work out where it is, when it is active, and how to find it, then go and do that properly for several nights running.
I have surveyed butterflies and bats, run camera traps and point counts, and worked reefs and mangroves as well as rainforest. Five biogeographic realms so far. That breadth is why I am rarely standing somewhere with no idea what is in front of me, and why I can usually tell you what will be next to the thing you came for.
Where a group needs a specialist I do not have, say a taxonomist for an obscure invertebrate group, I will tell you and find one, as I do with birds.
Photography-led trips
Not a different subject, a different pace. Fewer species, more time with each: waiting, moving round to the other side, getting the light to work, and not walking off after ninety seconds. Groups cap at four or five instead of six, because six people cannot photograph one frog.
The slow pace is the point: a photographer who is hurried goes home with nothing. The ethics are not relaxed for a photograph: nothing is moved, chilled, baited or staged, and a picture of an animal where it actually was is the only kind I will help you take.
How to ask
Tell me what you want to see and roughly when. If it is something I can do well, I will say so and build it. If it needs someone else, or a season of groundwork first, I will tell you that instead and give you a date rather than a promise.
Tell me what you want to find
A shortlist of ten species is more useful to me than “snakes”. Planning costs nothing, and the more specific you are, the more useful my first reply will be.