Hmm, where to start? I would say that most of the SC questions posted here are tougher than the ones you will encounter in OG, Kaplan or PR. The reason being that they have been carefully screened and selected to ensure a decent difficulty level once posted; there would be no point in posting easy problems here. Do not worry too much if you do not totally understand all SC questions because certain question quality are really dubious (ie the one with "the chinese commoner inside the heavenly palace")
First, try to spot the most common errors:
- pronoun errors
- misplaced modifiers
- parallelism
- verb tense
- subject verb agreement
- idioms
Once you mastered the above concepts, you will have to look at second order analysis. By that, I mean trying to understand what the sentence is trying to convey. Something that is often crucial in making a sentence clear is knowing when to use a participial phrase or a parenthetical element for instance. You might want to use this link to learn about those above concepts:
https://webster.commnet.edu/grammar/phra ... participle
Some examples about when to use participial phrases are here:
https://www.gmatclub.com/phpbb/viewtopic.php?t=7578
There is also the problem about the "sun clock" which I don't have the link handy here.
A link to the use of parenthetical elements:
https://www.gmatclub.com/phpbb/viewtopic.php?t=7232
Knowing about elliptical clauses, restrictive/non-restrictive clauses is also very useful.
A link to ellipses:
https://www.gmatclub.com/phpbb/viewtopic.php?t=7635
A link to restrictive/non restrictive clauses:
https://webster.commnet.edu/grammar/clau ... estrictive
This of course is for if you want to REALLY master SCs. Given that you have the gift of time, I would learn those concepts. The "second order analysis" is something I did not, to my own detriment, master in my last attempt. Do not make the same mistake and learn those above mentioned concepts.