Before you commit to the full brew, check your grind size: if water drains too fast, grind finer; if it clogs, grind coarser. Watch the bloom: a vigorous, even bloom indicates fresh beans and good extraction. Taste your first sip—if it's sour, your water is too cool or grind too coarse; if bitter, you're over-extracting. Adjust your ratio or technique for the next cup.