How long before applying for credit after late payments

I went back to school this past september and as a side effect my income dropped. I had about 4 months of late payments (credit cards and utility bills mostly) the mortgage has never been missed for the last 10 years and my credit score was around 750 before I started having trouble. I am carrying credit card debt that I am working on paying off and this whole situation has smartened me up so now I am planning to try to get out of debt within the next 3-4 years.

I also just renewed my mortgage and did not have an issue.

My question is how long should I wait to apply for other cards or some sort of consolidation loan? I am not looking to run up more cards but shift the high interest debt to lower interest.

Thanks for any input.