The first rule of meeting and greeting is safety.  Small dogs are at risk not only by virtue of their comparative size, but also of being mistaken for a squirrel.  You can never be too careful - you just don't want to seem worried.  Be calm and positive.  If you panic, so will your pup!  Even with my larger dogs, I never take chances.  I have a 1.5 year old 20 lb. dog and I slowly scoop her up and move away if she's at risk.  If there's an oncoming dog and they are on leash and under control, I make a large curve around their path of travel to increase distance so my dogs feel safe and it's clear to the person that we aren't interested in meeting.  Sometimes I cross the street, so we don't have to pass in tight spaces.

It took a while for my small pup to hop into the car by herself.  (She was also a little reluctant because the car made her queasy.)  As her tummy settled and she got to go more fun places, she became more eager and started making the jump herself.  She wore a harness so I could be ready to spot her and assist as needed. In the meantime, we did lots of practice in the house, hopping on and off foot stools for treats and we walked on railroad ties around the garden and at the park to increase her confidence. We parked the car close to the curb and worked on hopping from the ground onto the floor of the car for treats, because a vertical leap onto the seat was just too high.  She still needs a run at it, even now, and I still lift her into the back of the SUV.

As for greeting dogs you don't know - I avoid off-leash dogs like the plague and generally say, "no thank you" when someone asks if their on leash dog can say "hi" if there is ANY doubt in my mind that the dog is questionable or the person isn't capable as a trainer to know when to call their dog out, or if the dog would come if they did.  (And remember, I have years of practice observing thousands of dogs and people and I rarely say yes!)  And, even if the dog was clearly fine and the person was awesome, if my dog says, "no thank you" my answer is "not today!"  I would never ask my dog to forsake her feelings of fear or safety so I can let another dog invade her space.  I want my dogs to know that I will always listen to their needs and keep them safe.  They always have the option to avoid situations that worry them.  When they know they can leave if they need to, they will be much more apt to show interest the next time, because they feel safe in knowing that you will help them opt out if they change their mind.

This article is about Over-stimulated, Overly-Friendly dogs, but I want you to look at the picture of the overly friendly dog greeting a small dog and remember that picture when another dog wants to meet yours.  This is a greeting Larry does not want to have.  Then compare that picture with the video that I have attached with the tiny Pomeranian interacting with the larger pup.  Note that the handler of the larger pup is keeping their leash low to avoid lifting the dog's posture and is limiting the distance, but not keeping the leash tight.  The man with the Pom is allowing the pup to approach if he wants and retreat to take a break.  This is week four of Puppy Preschool.  On the first week in the classroom, Mushu the Pom hid under the chair or shivered on his mom's lap.  He bluff-rushed, barking at every dog and human who showed him any notice or got too close. He's still cautious with strangers but worked with us a little in class and felt comfortable playing near the neutral owners of his chosen playmate.

Here is another article to help you help build Larry's confidence: Helping Your Worried Dog.

Between 7-9 months adolescent dogs go through a normal secondary fear period where they are more easily startled.  So a certain amount of caution and startling at wights and sounds is typical.  I label anything that might be concerning in my cheerful voice and let them know if there's something coming that might startle them so there are no surprises that catch them off guard.  Example:  "boof boof" worried look - "Yay! It's the mailman!  Let's go see what he brought us!"  or "Big truck, yay!" "Here comes an Airplane!"  "Look Arbee, it's a kitty on TV!"  (Yesterday, she lost her mind over a cat food commercial because the cat was peering over a countertop and suddenly jumped.)  Early on, I scattered treats for her to scarf up right after I announced what she saw or heard.