Tight focusing with very small f-numbers is necessary to achieve highest at-focus irradiances. However, tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target irradiance. We describe several near-infrared, visible, ultraviolet, soft and hard X-ray diagnostics employed in the ~10²² W/cm² laser-plasma experiment. We used ~10 J total energy femtosecond laser pulses focused into a ~1.3-µm focal spot on 5–20 µm thick stainless-steel targets. We discuss the applicability of these diagnostics to determine the best in-focus target position with ~5 µm accuracy (i. e., around ½ of the short Rayleigh length) and show that several diagnostics (especially, 3ω reflection and on-axis hard X-rays) can ensure this accuracy. We demonstrated target positioning within several µm from the focus, ensuring over 80% of the ideal peak laser intensity on-target. Our approach is relatively fast and does not rely on coincidence of low-power and high-power focal planes.