It will soon be fa-la-la season for holiday parties, but there’s one celebration that happens any time of the year — the birthday party. Some parents may aspire to throw a bash for their child like pre-divorce Tom Cruise and Katie Holmes did in 2006 for their Suri’s second (!) birthday, splurging $100,000 on fresh flowers ($17,000), Wolfgang Puck catering ($45,000), a $5,000 cake — not to mention other extravagances like filling the house with 1,000 butterflies! But most of us don’t sail in that stratosphere. That’s where our party primer comes in, brimming with helpful steps to a fun but sane celebration, whether planning a party at home or trying to find an entertainer or the perfect party place. There’s also advice on proper party preparations and etiquette, and how to strike just the right tone for those persnickety teen celebrations. So, all together now: “Happy Birthday Party to you…”