Answer :
Here is some advice using 'should' or 'shouldn't' for the situations you've mentioned:
My running shoes are too small.
- You should consider getting a new pair of running shoes that fit you properly. Wearing shoes that are too small can be uncomfortable and might cause blisters or other foot problems.
I really want a pet!
- You should research about different pets and their needs to see which one fits your lifestyle. You shouldn't rush into getting a pet without understanding the responsibilities that come with it.
I've got nothing to wear to my friend's party.
- You should look through your wardrobe to see if you can mix and match items for a new outfit or consider borrowing something from a friend. If necessary, you should think about buying something new within your budget.
I don't know the way to the museum.
- You should use a map application or GPS to find the best route. You shouldn't hesitate to ask someone for directions if you're unsure.
The weather's really hot and I want to go to the beach.
- You should make sure to pack sunscreen, a hat, and plenty of water to stay safe in the sun. You shouldn't forget to check the weather forecast to ensure it's safe to spend the day at the beach.