Go to the park, figure out who goes alone, chat to them.

Go to a coffee morning and make friends not based on who your child plays with.

Take long walks and chat to all and any interested strangers.

Join a group - church service, art group, book club - anything where you get to meet people.

Ask the local baby shop if they do network evenings: mums get to meet each other and peruse the shop with a drink.

HTH, I have needed a mixture of all of these but have some decent friends now.