When Washington took command of the American army at Cambridge in 1775, his troops were mostly untrained men who - ostensibly - were no match for British professional soldiers. Even Washington himself did not have the training of his counterpart, General William Howe.
On the other hand, the patriots were filled with determination. Longing to be free, they would fight the war their way, not the British way. Guerilla tactics, ambushes, and refusal to fight in straight lines (like the British), helped the colonists to hold ground.
Not all Americans agreed with the fight for independence, however, especially at the beginning of the revolt. For many people, England and the Crown represented a stable way of life. Why should that authority be challenged? As military leader, Washington had an extraordinarily difficult job ahead of him.
A meticulous man, the General kept records as carefully during the war as he had kept them during his school years. However, he had one constant, personal hardship: bad teeth. (He ended up with false teeth, made of hippopotamus tusk - not wood - which were too big for his mouth. A set is displayed at the National Museum of Dentistry.) Even during the war, he wrote letters to his dentist. (Follow the link to one such letter which was intercepted by the British.)
As Boston remained under siege in 1775, the Americans desperately needed more arms. The British had plenty at Fort Ticonderoga (near Lake Champlain and the Canadian frontier).