In the episode First Contact, the Enterprise is in orbit around the planet Malcor III, a pre-warp society that is planning to launch their first warp-capable vessel in a year. The implication behind this would seem to be that the Malcorian are capable of launching objects into their own orbit and would also be able to detect objects in their planet's orbit as a result - if not by radio transmissions, then certainly visually as with telescopes. Meanwhile, the Enterprise is in orbit in order to make a careful first contact with the Malcorians and to locate an injured Commander Riker who was on the planet.
There are other episodes throughout Star Trek with similar setups (a starship in close proximity to a pre-warp society and forced to interact covertly), such as the Voyager episode Blink of an Eye where a pre-Renaissance society is able to detect and (mostly) identify Voyager throughout its accelerated development - first as merely a star, and then later as an actual object. In another Voyager episode Future's End, Voyager is sent back in time to 20th century Earth where a civilian astronomer is able to initially detect the ship in orbit because of its radioactive emissions. Granted, both of these involve scenarios where Voyager is damaged or trapped and not necessarily able to actively avoid detection, but it certainly demonstrates that detection is reasonable if the starship merely entered orbit and took no special precautions.
However, Federation vessels are not generally permitted to use cloaking technology to hide their presence. With regards to our own experience with the International Space Station, the ship could presumably be seen visually through telescopes (the ISS is about 110 meters across, while the Enterprise-D is at least 550 meters based on "twice the length... of the Constitution-class ships"). So absent a cloak, it would seem quite plausible for amateur astronomers to see a starship in orbit with a simple optical telescope, let alone any professional astronomers with much more advanced and powerful radiometric devices.
So what precautions or technologies does the Federation have to avoid detection of their starships by pre-warp societies in scenarios where they still need to interact with the planet and/or its societies? Specific concerns would be avoiding detection of their ship visually or by its radioactive emissions, or any other method we see a starship being inadvertently discovered by such.
EDIT/Clarification: There are some cases where the solution seems to be "Let them be seen, but hope that anyone who does will be dismissed as a conspiracy theorist", which was essentially the resolution from the First Contact episode. I'm interested in whether there are solutions that result in effectively perfect non-detection - such as the holographic "duck blinds" from Who Watches the Watchers - rather than just reducing the potential number of people who might have seen them without actually preventing it.