Fries: Best potato variety is called Nicola. Fry once at 160°C for 4-5 minutes, depending on size of the fries. Let rest for 30 minutes. Fry at 180-185°C for at least a minute until crispy golden brown. Traditionally served with salt, mayo and Belgian pickles.
Croquette: make (firm consistency) mashed potatoes, roll through beaten egg, then through breadcrumbs, shake off excess breadcrumbs (else your frying oil gets ruined). Fry until golden brown at 180°C. You can add grated cheese or truffle to the mashed potatoes, shrimp, chopped herbs (chives, chervil, tarragon,…), or leftover chicken. You can replace the breadcrumbs with panko, or you can add poppy seeds to the crumbs. What's important is that you keep an eye on the consistency of your mashed potatoes, else they'll fall apart in the frier.
Fried cod, turbot,…: cut a filet of cod or whatever into slices, beaten egg, bread crumbs, fry as above.
Beignet: dip chunks of fruit (apple, banana,…) into batter and fry as above. Cover with powdered sugar or honey. There's tons of (often regional) variations here as well, look around on the web.
Fried courgette flowers e.g. http://www.antonio-carluccio.com/Fiori_di_Zucchini_Ripieni