The fertile window matters more than total frequency
Conception is only possible during a roughly 6-day window ending on the day of ovulation, which makes timing relative to that window matter more than how often sex happens across the whole month. Ovulation tracking — apps, basal body temperature, or ovulation predictor kits — narrows down when that window actually falls for a given cycle, since it varies somewhat month to month even for people with regular cycles.
Every-other-day during the fertile window
This is the general guidance most commonly given: every-other-day sex during the fertile window balances sperm quality against opportunity better than either daily attempts or saving up for one big attempt. Daily sex during the window isn't harmful, but it doesn't meaningfully outperform every-other-day for most couples, and outside the fertile window, frequency doesn't move the needle on conception odds at all.
Two myths worth dropping
"Saving up" sperm by abstaining longer between attempts doesn't improve odds — sperm motility actually tends to decline with longer abstinence, which is part of why every-other-day beats a single saved-up attempt. And no specific position has strong evidence behind it for improving conception odds; timing relative to ovulation matters far more than which position is used.
When timing itself feels like the hard part
If tracking ovulation accurately feels uncertain, or cycles are irregular enough that the fertile window is hard to pin down, that's a reasonable thing to bring to a doctor rather than guessing. General benchmarks for when to seek help: after about 12 months of trying without success under age 35, or 6 months if over 35 — sooner with a known factor like irregular cycles or a prior diagnosis on either partner's side.