Clear the assumptions of the estimates
When you start to draft the numbers of your business plan calculations, you start to insert many data as input (primary data not deriving from other data) and be ready to distinguish them from the others (data derived from formula or a direct link from the input data). One suggestion is to highlight the cells containing the inputs with a different background (like light yellow). This helps the manager in surfing over the several spreadsheets keeping an eye on the assumptions of the projections, so the data that having been inserted directly represent the factors affecting the results coming from the financial schemes. However, not all input data are important at the same level: some have a relevant impact, others less or minimal. How to know about that? It is very simple: once the schemes have been drafted and we have the summarizing tables (usually, cash-flows, profit & loss, ratios), you go back, and change by little variations the values of the input cells randomly, one by one. If the results change dramatically, these inputs are relevant to your calculations (and your sensitivity analysis).
At this phase of the analysis, two further steps are suggested. One, if it is not too complicate and time-consuming, to gather all significant input cells in one unique separate spreadsheet, grouping all relevant data in a page as a dashboard for the management. Two, to advance the presentation of the numbers with a short chapter where you clear to the reader the main assumptions of your data, basically what are the major input values determining the forecasts.