Mostly, you will need to judge simply how much your own time may be worth. Inside general instance, you can get additional money per card by offering them as singles, or as tiny groups (such as for instance playsets of 4). However, that will simply take lots of time, particularly for a big collection. Dumping your whole collection at your LGS for a bulk price is exceedingly easy and quick, but you're not planning get anywhere near the maximum amount of money as offering each card independently on the web... but making all those on line sales takes a number of years and require lots of energy. (Shipping prices must also be viewed.)
Rares and old desirable cards are more fluid, indicating it's not hard to find some body ready to purchase them, which means that less time and effort spent attempting to sell them. Foils may or might not be liquid, according to the cards involved.
I actually do not recommend selling loose old packs on the internet. When you look at the extremely oldest units, it is possible to figure out the exact contents of this pack before opening it, meaning the savvy buyers will will not buy any packed old cards unless they're in a factory-sealed box/case. (The presumption becoming that seller has determined the pack includes nothing of well worth currently.)
Even yet in the units new enough in which that is not feasible, package mapping happens to be something for many years, therefore a vendor could grab all of the worthwhile packs from a field before offering the rest; Wizards made efforts to counteract this over time, but they have only really already been efficient within the newest units (roughly Avacyn and onwards - mapping continues to be possible, but it is no more financially beneficial). The possibility of repacks additionally tends to make on line buyers cautious with purchasing free packages from older units.