Someone on reddit asked for a guide for all the warning signs. I will update this as I think of more/encounter them in-game, but I think the most important ones are here. The screens were taken in Invasion but are also valid in PVP/PVE. Thank you to ErikErikson for the help.
There is also a counter for number of people locked onto you but I couldn’t find a second volunteer.
“Pinging” targets: used by pressing the middle mouse button, double-pressing the “Lock Target in Crosshairs” button on your keyboard, or pressing the “All eyes on target!” key if you have that one bound. This is used by your allies to signal important targets to you, including ships, beacons, bombs, and gates and structures in Invasion or PVE.
This red circle is also used automatically in the game mode Beacon Hunt in order to signal the next beacon to go to. It signals this 20 seconds before the next beacon is activated. (print screen coming when I next get a beacon hunt match)
There is a warning called “targeting system malfunction” which pops up when someone uses White Noise (cov ops) or IR Pulsar (LRF) on you. This means that you cannot lock onto enemies for a certain duration. Remaining time is shown by the countdown. (print screen coming).
Across the top of the screen in the middle can usually be found a lot of logos with buffs/debuffs that are currently acting on your ship. This can be either by allies, by enemies or by yourself. Mostly the icon is the same as the module that applies the buff. If you do not recognise an icon, press enter to get your mouse, and hover it over the icon. A tooltip describing the effect and with important numbers will appear. I will try and get some print screens of some of the ones that are hard to recognise.
There is a bright red warning when your hull strength is very low, but by that point you are probably more concentrated on getting away and staying alive than on your HUD, and I don’t think I can get a print screen…
There are also sound warnings which are harder to show here, and are usually self-explanatory anyway!