Get as close as possible to the subject. The biggest problem I see with insect photos on iNat is that they are taken from much too far away. Most insects (with the exception of some social hymenopterans) are not aggressive and are unlikely to want to harm you unless they feel directly threatened. Phone cameras are typically not good at taking detailed photos from any distance, with “distant” being much closer than one might think – I recommend well under a meter/a foot or two at most.
Consider using flash if indoors. A greenhouse may seem light to us, but it is not very light for a phone camera with a tiny sensor.
Waiting quietly by a blooming plant is often a good way to get photos of bees and butterflies and other flower visitors, because they are occupied with flower visitation and are more likely to stay still for photos. (I’ll note that I find bugs and beetles and other relatively slow-moving arthropods much less frustrating subjects for phone photography than bees, butterflies, or odonates.)
Avoid casting a shadow on the subject, as many insects will startle and the light metering of the camera is more likely to struggle when presented with a mixture of shadow and sun.
If capturing insects and photographing them through the container, please make sure the container is highly translucent and the camera is focused on the insect instead of the outside of the container. Some insects may be photographed in hand, but I don’t recommend doing this unless you are familiar with the insect in question and know whether this is safe (e.g., male bees can’t sting, but you have to know whether it is a male or not…). Captured specimens also do not generally make particularly interesting or aesthetically pleasing photos; this is more a strategy for photographing for ID.