tablespace full

hi

can anyone suggest me what are the steps need to be performs next.in order to solve the issue,here is the issue

Tablespace Size (kb) Free (kb) Used (%) Tab/ind Extents Status AutoExt (kb) Used (%)

PSAPBTABI 643.590.912 50.224 99 5.958 47.492 ONLINE 718.427.152 90

thanks in advances