Yesterday I brewed an English Bitter, which I mentioned here, and the first one since I decided to make a few changes on my brewing procedure (such as; different water, better check of temperature for both mashing and fermentation) The brew itself went pretty smoothly and for the first time I used liquid yeast mentioned in the above link, Wyeast ESB 1968. However, it's 24 hours since pitching now and I can't see neither air lock activity nor any visible krausen in the fermentor. I followed instructions on the yeast pack, smacked the nutrient bag, shaked, and let it all sit in room temperature for a 3 hours. I pitched in somewhat too cool wort I think, it was close to 16.5 C (62F) instead of the expected 18C (64F), that was last night 8pm or so. This morning the temperature was 20C (68F) which I intended to keep for some days. Thinking back, I did aerate the wort before pitching, shaking it quite a bit, but I don't think I did anything after pitching. I just poured the yeast in and sealed with the lid. Is there anything I should do, any actions to be taken? Or sit and wait and hope for the best?