We have established new guidelines for the collection, fitting and interpretation of magnetisation relaxation times derived from DC decay measurements. After calibrating the magnet, we advocate continuous VSM measurement through the field change until the moment has reduced to at least 0.01M 0 in the target field (measuring to at least 0.1M 0 for very slow relaxing samples). If VSM mode is not available, then continuous DC scans with a short scan time are the second preference. Magnetisation decay data should be fit to Eq. 2 with M 0 fixed to the first point measured in the target field and M eq fixed to the calculated target value; only the decay is measured to ≤ 0.01M 0 can M eq be reliably freely fit. The relaxation time from magnetisation decays is best described by e ⟨ln [τ]⟩ (Eq. 9), with ESDs defined by the logarithmic variance (Eq. 13). This measure of τ is com- We find that both DC magnetisation decay and long-timescale AC waveform techniques can be recommended for measurement of relaxation data. Magnetisation decay measurements are limited by the time taken to change the field, restricting the recording of faster rates, and potentially biasing broad relaxation distributions. On the other hand, the square-wave method is the gold standard, but as multiple oscillations are required on a time-scale appropriate for the magnetisation relaxation time, the required experiments can be incredibly long.