When smiling at someone, pause first before visibly moving from neutral expression to "flooding smile." This sends a message that your smile is in response to seeing them and giving them a positive impression that you find them special.
Keep near-constant eye contact with the other person, even when they're not talking. If you look away, do so slowly and reluctantly.
Same as Sticky Eyes, but keep watching the other person even when someone else is talking. A more subtle version of this is bouncing your gaze to your target when another person finishes speaking, showing you're interested in their reactions.
For better posture when entering a room, imagine an iron-jaw bit hanging from the door frame. Bite it and let it pull you up to a tall, strong posture. If this doesn't work, imagine a string on your chest pulling your forward and upward, at around a 45-degree angle.
When being introduced to, or meeting someone, make a large pivot towards them. Point your body towards them, smile wide, and give your undivided attention. Another good way to subtly tell someone you find them special.
When meeting someone, imagine you're reuniting with a long lost friend. This helps position your body language and communication to be much more relaxed and familiar.
Avoid fidgeting, scratching, squirming, or any related behaviors when talking with others. These give the impression you're lying or being dishonest, even if you're not.
Always watch how your target is responding and reaction to a conversation. Adjust the topic, and your body language, accordingly.
Visualize steps 1-8 in advance whenever possible to boost your confidence and improve execution.