  Order parameter fluctuations (the largest cluster size distribution) are
studied within a three-dimensional bond percolation model on small lattices.
Cumulant ratios measuring the fluctuations exhibit distinct features near the
percolation transition (pseudocritical point), providing a method for its
identification. The location of the critical point in the continuous limit can
be estimated without variation of the system size. This method is remarkably
insensitive to finite-size effects and may be applied even for a very small
system. The possibility of using various measurable quantities for sorting
events makes the procedure useful in studying clusterization phenomena, in
particular nuclear multifragmentation. Finite-size scaling and delta-scaling
relations are examined. The model shows inconsistency with some of the
delta-scaling expectations. The role of surface effects is evaluated by
comparing results for free and periodic boundary conditions.
