Am pretty new to home brewing and have run into the problem of not having much carbonation in my beer. It tastes Good, but a tad flat; and the head in the beer is basically non-existent. One of the batches I made was from a kit, the other two were recipes I found on home brew talk. I used an 8oz (or whatever amount that comes in the individual packets of priming sugar) but I have had this problem with each batch. After bottling I let the beer sit in 70 degrees for two weeks, is there anything else I can do to fix this issue?