Shime-saba, because it's been marinated in vinegar, has a particularly strong fishy taste to it; which can really offset most diners. There are a few varieties of mackerel that are commonly sold in the market. King Mackerel, Spanish Mackerel, and Boston Mackerel. Most saba that you see at the sushi-ya is more often than not of the boston variety (usually pre-made).
However, for the true connosieurs out there, I'm going to provide a personal recipe for preparing Shime-saba:
Using a whole mackerel, fillet it on both sides and discard teh guts, spine, and head. Sprinkle heavily with sea-salt on both sides of each fillet and let sit for one hour and thirty minutes. Rinse off salt and peel off skin. Then in a 1:1 solution of rice vinegar and water, marinate for twelve minutes. Wrap, first, in wax paper, then plastic wrap for storage; or debone then slice for immediate service.
For service, I personally love saba served w/ a pinch of freshly grated ginger and sliced scallions. You can also grill the fillets w/ lemon and serve w/ scallions as an alternative.