You will very likely feel time pressure on the reading section. You cannot afford to spend too long reading any particular passage nor answering any particular question. Keep your eye on the time and force yourself to move along.
Of the five reading passages, by far the hardest for most kids is what I call the Old Text passage (the SAT term is “Founding Documents and Great Global Conversations”), written long ago, even hundreds of years ago. The writing is hard to understand and typically the subject matter is, too. Normally this is the fourth passage. Do it last.
Here is the wild card: the first passage, the fiction piece, can ALSO have been written long ago and therefore pose much the same difficulty. How do you know how old it is? Look for the date in the blurb that precedes the actual passage contents. Point one: if your fiction piece is old text, do it second-to-last. Point two: if you are not good with fiction, do this passage second-to-last even if it is not old text. If you are completely comfortable with fiction and have done well with it on practice tests and it is not old text, then OK to do it first.
The second, third, and fifth passages normally are on the easier side and so can be tackled early.
Read each question carefully. I am repeatedly amazed at how frequently students get questions wrong because they make unforced errors understanding exactly what they are being asked. E.g., missing a crucial word like “not” or “except.”
Remember the Golden Rule of SAT reading: the correct answer is always provable from the text. Think rigorously and logically. Be demanding – if any part of an answer is wrong, even just one word, then the whole answer is wrong.
Get a good night’s sleep. Wake up at least an hour before the test. Have a good breakfast. Go in prepared to do battle. Keep your focus for the duration; rest comes later. Good luck!