It is very important to be familiar with common conjuncts in Hindi. A conjunct is when two consonants combine together, eliminating any vowel sound in between. In English, the x sound can be written ks. There are two ways to write this in Hindi. The easiest way is to add a slanted line, called a virām, under the first letter. This indicates that there is no vowel sound between the two consonants.
This way is very simple, but unfortunately it is not common. The more common way is to just remove the right portion of the first letter (usually the vertical line) and stick it next to the second letter.
Here are some more examples.
This rule will work for most conjuncts, but conjuncts with 'r' are formed differently. The first type is called the flying 'r'. This is used when the first of the two letters in a conjunct is 'r'.
र् r + क k = र्क rk → पार्क pārk
र् r + द d = र्द rd → दर्द dard
The second type is used when 'r' is the second of the two letters in a conjunct.
क् k + र r = क्र kr → क्रम kram
त् t + र r = त्र tr → पात्र pātr