You may check options reports at investment-tools.com. There are couple of repors that list options with high probability of profit for sellers of the options. In essence they are options with low probability of profit for buyers based on options pricing model. That is a free site.
If selling premium that is not covered by owning the underlying, then you must post margin in case it works against you.
You need to get hold of an options book like the old one that George Angell(shady character) had written (Ag options mostly, but the basic principles are there). At this time, I would recommend that you do not try to get into Riskarb's posts as they are well beyond your understanding at the present time. Riskarb has tremendous mathematical acumen and of course I have respect for him, but you won't need the full blown math to begin the process or later on to be successful.
Correct--by buying it back , you are just offsetting your position at he particular strike. For example you may have sold a 100 call which would require you to deliver at 100, but if you buy an option at 100 call option later, then you now have the right to"call" someone elses away and you would be able to deliver. Thus, the positions offset and you are no longer on the hook to deliver.
One more point about covered calls. They are passed off as being "safe". What this means is that you will lose a little each time and eventually gradually lose it all. Why not make a little each time and gradually be wealthy?
Because you keep selling OTM options and collect those lovely premiums, and then finally on one trade the OTMs become DITMs and all your previous profits were wiped out.
The answer to that is the overextension argument that I have been making. If not overextended, this will not happen.
In that case, the profits will still be wiped out, but you still have a major chunk of your trading capital.
The difference in our thinking here is that without being overextended, I would be selling more new OTM strikes and increasing those in quantity. I will have time on my side and at expiry, I will make a lot of money. This is one of the secrets to short options. Don't be greedy with the first entry. Give yourself room to add. It's easy to get greedy--you like to see the money in your account. The trades that go against me--occasionally wildly-- are my big winners.