Before switching from FULL to SIMPLE recovery model, ask yourself how much data you can afford to lose. For the databases where in case of a disaster you're fine with restoring the last database backup, SIMPLE should be OK. If this is not the case, stay with FULL

To shrink the LDF file to as small a size as possible, follow the steps given by Kimberly Tripp here: 8 Steps to better Transaction Log throughput

1. Wait for the time when there's low activity on the database

2. Run in SSMS

   DBCC SHRINKFILE(transaction_log_logical_filename, TRUNCATEONLY)

3. Modify the transaction log file size

   ALTER DATABASE db_name MODIFY FILE ( NAME = transaction_log_logical_filename, SIZE = new_size)

Before switching from FULL to SIMPLE recovery model, ask yourself how much data you can afford to lose. For the databases where in case of a disaster you're fine with restoring the last database backup, SIMPLE should be OK. If this is not the case, stay with FULL.

To shrink the LDF file to as small a size as possible, follow the steps given by Kimberly Tripp here: 8 Steps to better Transaction Log throughput

1. Wait for the time when there's low activity on the database

2. Run in SSMS:

   DBCC SHRINKFILE(transaction_log_logical_filename, TRUNCATEONLY)
   

3. Modify the transaction log file size:

   ALTER DATABASE db_name
   MODIFY FILE ( NAME = transaction_log_logical_filename, SIZE = new_size)