After you have evaluated the mesh using visual inspection, mesh statistics and mesh diagnostics, you can edit the mesh to fix small identified problems. If the problems are too important, remesh the model with better parameters in order to have a clean model before you run an analysis.
To fix mesh problems, you can use the Mesh Repair Wizard which runs a series of diagnostics on your model and, for each diagnostic, enables you to fix most problems detected automatically.
Alternatively, you can use the mesh edit tools to fix any problems you have identified from the mesh statistics report.