As a canning instructor, I have noticed that most people get interested in canning when strawberries show up at the farmer's market in June. The first impulse is to try to make strawberry jam, which actually is one of the harder things to make. I always recommend that folks start out with something simpler like a pickle. It's hard to mess up a pickle, but pretty easy to screw up a jam - it burns easily, it takes practice to know how if there's enough pectin involved so the jam will set up, etc. But perhaps the best thing for a novice canner to try might be citrus. After all, the citrus season is winter, and there's not much else to can in wintertime, and often folks are spending lots of time inside anyway. Why not spend it in the kitchen?
To learn how to can, I suggest getting a really good canning book - there are tons of canning books out there because all the hipsters are in to canning these days, but my go-to book I recommend is the Ball Complete Book of Canning by Judi Kingry and Laurie Devine. This IS NOT the "Ball Blue Book", which is really just a canning magazine that is issued yearly. There's nothing wrong with the Ball Blue Book, (or as my friend Ann and I like to call it - the "Blue Balls Book", because our sense of humor is permanently stalled in the 7th grade) but for the price, the Ball Complete Book will teach you how to can in exquisite detail and it offers many helpful canning tips you won't find in the magazine. It also has lots of interesting recipes in it. There's also a trusted online source you can check out - the University of Georgia's National Center for Home Food Preservation, but I find the book much more user friendly.
Last year, I canned grapefuit and we loved it so much, I made some again this year. I experimented with a different technique I read about online for peeling grapefruit - it worked like a charm! All that you have to do is put the unpeeled grapefruit in boiling water for about 5 minutes. The peels come off easily and leave very little bitter pith behind.
Crimson Honey Grapefruit (printer friendly)
(makes about 9 pints, more or less)
1 large bag (18lb) grapefruit - I used ruby red grapefruit, but any kind would work
1 large can frozen cranberry cocktail, thawed and undiluted
2/3 c. honey
Peel grapefruit as described above. Cut each fruit laterally (side to side) in 1/4 inch slices Measure fruit and juice until there's 16 cups. Mine came out almost exactly that for an 18 lb bag, but it depends on how big the grapefruits are. Don't worry too much. If you end up with more, you could make some more syrup, or less, you can use less. Note that grapefuit is acidic enough to can on it's own without anything added - the cranberry honey syrup is for color and flavor, so don't worry too much about exact proportions. If you want to make it sweeter, add more honey.
In a large dutch oven (or a big pot), heat up the grapefruit and it's juice, the cranberry cocktail syrup and the honey and heat until the honey dissolves. Using a slotted spoon, pack hot grapefruit into hot jars (I used pints) until you have 1/2 inch headspace. Ladle some hot syrup in, leaving a half inch or so, and use a cocktail stirrer or a chop stick to get the air pockets out and add more syrup if you need to. Wipe rim, put on the lid and band and tighten until fingertip tight. Process for 10 minutes in a boiling water bath canner. Remove canner lid and let jars sit for 5 minutes, then take them out of the canner and let them cool for 24 hours. If you have extra syrup, save it. It makes a pretty grapefruit cocktail by shaking it in a cocktail shaker with some crushed ice and vodka.