Teach explicitly capitalization rules to the whole class. Focus on one or two rules at a time. Start with capitalizing the first word in a sentence and capitalizing proper nouns. Distribute capitalization practice sheets, so that the students can work on this lesson.
Model correct capitalization on the board. Also, write sentences incorrectly on the board and invite students to correct them.
Introduce one or two capitalization rules each week. Practice the newly introduced rules, along with previously taught spelling rules.
Remind students to check their work for proper capitalization before they turn in their assignments. Allow students to exchange papers and also check each other's work for capital letters.
Conference with individual students to discuss any capitalization rules the students may not understand, as other students do independent work.
Allow students to revise their work and correct capitalization errors before they submit a final copy of their work.