My standard sangria
Note: DHP-size recipe is double what I list below. Adjust as appropriate.
Take one large bottle of Fairbanks port, the big cheap bottle. Take one bottle of decent red dinner wine - I usually use a pinot noir or a cabernet, but the important thing is not to spend noticeably more than $10. Go to the local safeway, and see what fruit looks 1) good and 2) slightly overripe. Especially good are: strawberries, cherries, star fruit. Also pretty good: oranges, apples, kiwis.
Pour the two bottles of wine together into a pot. Put the fruit in, cut appropriately. 'Appropriately' means 'ready to soak up alcohol'. For citrus fruit, slice normally. For blackberries or raspberries, you're probably fine - nice high surface area. Small things with skins like cherries, blueberries or strawberries should be sliced a bit, or maybe halved. The important thing is that it be able to soak up lots of wine.
Marinate just like that for one to two days. Cover if necessary. Then serve by itself, or with sprite or ginger ale as a mixer.
Oh, and I forgot when I emailed her, but maybe she'll see it here: the more fruit, the better, as long as you've got enough wine to cover. Lots of fruit means really intense flavor. Strawberries and cherries make *incredible* sangria if you can use lots.