While both having TAs and being one for several classes, I had found that the two rules for effective TA-ing is to (1) Not give out the answers and prompt investigative thought, (2) Make them feel like every question they ask is interesting, and (3) Do your best not to be presumptuous about what students retain from prerequisites.
First off, it will be tempting to fill a void of silence when prompting discussions or during one-on-ones. Every student will want to jump straight toward the solution and see if they can draw the connecting lines later. Prompt them to think. Ask tricky questions to tease their understanding and make them consider factors they might be missing. See if they can apply that logic to the main problem. (*For instance, I was lecturing about the isomorphisms that can be drawn between physical systems like a damped RLC circuit and a frictional mass on a spring. They were having a difficult time understanding the factors and concepts in the RLC circuitry equations, so I distilled it down to general behaviors like "what is losing the energy in the system", "what here behaves like inertia, resisting change", etc*.) If you equip them with the tools to solve the puzzle, all you have to do is reframe and tease until they understand.
Second, asking questions is daunting. Be friendly, be respectful, and acknowledge how interesting a question can be. Students who feel comfortable asking questions inevitably ask amazing questions in class. You're in this field because it is a fascinating field. Act like a question asked to be re-explained for the hundredth time is just as interesting as the first time. Find relatable examples, invite them to ask more, and always follow-up. I often started these sessions out with, "Now, if you think you're missing something or are trying to remember something form a previous class, there are half a dozen others in the same boat. Do them a favor and ask."
Lastly, and what I've found to be most important, is not to presume what students have retained from previous classes. I've had students who have forgotten basic trig identities, major assumptions behind statistical tests, etc. Check-in constantly, ask, "Does anyone need a quick recap on L'hopital's rule?" "Is this feeling a bit rusty to anyone right now?" Communication is important.