Apple Cider Vinegar mixed with some distilled water and taken daily on an empty stomach will increase stomach acid over time. Probiotics and kefir also helps to increase stomach acid content as well.
Alcohol will diminish most all micronutrients and B12 production as well, so avoid that. Meat-eating doesn't necessarily inhibit B12 production, but it will if eaten WITH a starchy food at the same meal: avoid proteins with starches at the same meal basically.
Allowing the stomach to rest till lunchtime after a good nights sleep and having a brunch will rest digestion and allow it to become more efficient by producing more acid as well.