best tactics to increase credit ratings?

Sounds like you should have an excellent rating already, barring any recent trouble on your record. I would be surprised if your credit score is not already 800. To go even higher, you would probably need to acquire additional assets, like income properties.

A credit score is based on a 12 month activity and goes up 5 to 10% per month providing you are paying on time. If you have 24 months of activity, then you're probably between a good score (660/749). If you have a mortgage that will be paid off shortly and can show 12/18 of employment, your best option is to get a secured credit line from your bank. The rates vary from 2.5 to 5.5% which is a good rate. You'll get your answer with 1 to 2 days.

Wait for credit card statements of $0. Sometimes there is some "left over interest".

Then, use one card for gas, and one for food.

This avoids interest and keeps usage alive.

Also a good way to track yearly spending on gas and food.

You can achieve excellent credit just by doing this.

Next goal: 5 months of income in a Savings Account.

In case you lose a job, have medical not covered by insurance, or have car repairs.

No one should live without this. No one.