1) How to identify major s/r levels:
A) The higher the time frame, the more significant the level. An s/r level on a lower frame may be insignificant on a higher frame but an s/r level on a higher frame is significant on a lower frame. If you identify a s/r level on a 4 hr chart that is also a s/r level on the daily/weekly chart, thats an indication of a strong level
B) If the current swing low/high is the highest/lowest price has been for some time, its a strong level and will show up on higher time frames. If there is a recent swing low/high that is higher/lower than the current swing low/high, the level isnt as strong.
C) Major s/r levels were probably also major s/r levels weeks/months/years ago
2) How to draw s/r levels:
A) I start on higher time frames, zoom out and begin by placing a horizontal line on the highest high and lowest low that may currently be in play.
B) Next, I move the crosshair up from the low or down from the high untill I find the next horizontal level that appears to be a good "fit" for my next s/r level. I look for horizontal levels with the following criteria: 1) levels where price tends to "gravitate" 2) levels that tend to act as support when price is above and act as resistance when price is below 3) levels that act as a base for a major breakout 4) levels that were approached by a major breakout without being violated by another high/low or a close above/below 5) support levels that become resistance and resistance levels that become support after a breakout thru the level 6) levels that are reached for or touched by long shadows
C) Move to a lower time frame and repeat the process above. I usually start with the weekly or daily then move down to the 4hr. I wont go any lower
D) When finished, open the time frame you execute on and clean up/ fine tune the levels.
Hope this can be of some benefit to you. Also, if you dont mind the suggestion...I highly recommend using higher time frames.
Best of luck to you.