适当形式填空是指根据句意和语法规则，在空白处填入正确的单词形式，包括词性、时态、语态、人称等。对于初一英语适当形式填空，需要掌握以下几个规律：
1. 根据主语的单复数和人称，选择正确的动词形式。例如：My sister (like) to play basketball. → My sister likes to play basketball.
2. 根据上下文语境，选择正确的形容词和副词形式。例如：The weather is very (cold) today. → The weather is very cold today.
3. 根据上下文语境，选择正确的介词和连词。例如：I'm interested (in) playing soccer. → I'm interested in playing soccer.
4. 根据句子的时态和语态，选择正确的动词形式。例如：He (write) a letter to his friend every week. → He writes a letter to his friend every week.
5. 根据上下文语境，选择正确的名词单复数形式。例如：There are many (child) in the park. → There are many children in the park.
总之，初一英语适当形式填空需要理解句子的语法结构和上下文语境，选择正确的单词形式填空。在实践中需要多读多写，积累语言知识，提高语感和语法意识。
