At this stage, I think it's not going to be easy at all to add much of any value to wrbtrader's two very helpful posts above, but for what it's worth (if anything) I'll offer my own perspective's answers to your original questions ...
It's clear from reading the forum (and any other forum) that very many traders do.
I identify swings-high and -low on timeframes higher than the one on which I'm trading, transfer them to that chart, and add current/recent ones, typically displaying them with differently coloured lines.
For my own purposes, I give most weight to (a) more recent ones and (b) multiple-touch ones, because my experience has shown me that these are the "historical" areas of S/R which are more likely to be repeated as "future" S/R.
I find it helpful to distinguish conceptually between "historical S/R" and "future S/R" rather than lumping them together as a more general/abstract category of "just S/R".
I tend to look at them as "approximate zones" rather than as "precise levels".
Parts of these questions are (for me) less strongly correlated to S/R than the questions above.
I enter according to various specific set-ups which arise from specific price action patterns, which are themselves all related to recent S/R. My precise entry is usually a tick or two above/below something you might call a "signal bar" which is part of a broader price action pattern.
I often avoid potential entries to trades which seem quite likely to me to encounter prompt, probable resistance (in other words, I don't like entering long just under what seems to me to be an area of reasonably probable future resistance, or short just above reasonably probable future support).
I sometimes add to
winning trades, because the fact that the price has moved in "my direction" sometimes strengthens my reason for being in the trade and increases the positive expectancy of the funds risked.
I exit typically in either two or three stages ("scaling out") according to the current volatility and the positioning of my initial stop-loss (also itself related to the current volatility).
I sometimes trail my stop-loss
manually on the part(s) of the trade still remaining open after partial closure, re-positioning it just above/below the most recently formed swing-high/low - that's S/R-related, too, of course.
Occasionally I use a line/zone of likely future S/R as a final exit (on the grounds that I can always decide to re-enter, if it's "unexpectedly" breached).
I'm interpreting your own wording above (perhaps mistakenly, perhaps unfairly) as coming from a perspective along the lines of trades having "specific indicator-determined signals, which are specific entries for trades" and that isn't a perception I share in my own trading. I tried that approach for 2-3 years but never found a way to become steadily profitable with it. I have an "overall bias" (by which I mean "times to try to identify only long/short trades from price action patterns) so that I'm almost always trading in the same direction as a longer-term trend. (I do also trade one "reversal pattern" of which that isn't
always true, though it often is.)
I don't use indicators now, but if I were using them, it would be only to identify my "overall bias", not to determine entries or exits.
All the long-term profitable traders I know (and know of), myself, who do use indicators, are using them just for "bias" rather than as trade entry signals. There may be ways of doing that profitably, but if so, they're outside my own experience.
I
strongly endorse wrbtrader's advice above about doing your own research, backtesting and forward-testing. It's
not trivial advice, and in my opinion some statistical/probabilistic understanding is a prerequisite to doing it adequately/productively (which is where/why many people go wrong with it, in my view, by trying to do it without first having learned how to do it
reliably, a skill-set none of us was born with and one that relates, after all, to a sometimes very counter-intuitive subject).
Whether any of this personal perspective is actually helpful to you is another matter.