Because God wants us to have lasting marriages and because long-lasting marriages bring the greatest happiness, it is important for us to choose carefully whom we marry. The principle of not being unequally yoked (2 Corinthians 6:14), is vital in this regard. While the passage in 2 Corinthians is specifically discussing the contrast between Christ and idols, the principle is likewise applicable to marriage. Marrying someone who shares our religious values provides a very important basis for compatibility.
Regarding baptism, we don't recommend baptism in order to get married. Baptism should be a separate, personal decision one makes because he or she wants to honor God and enter into a covenant with Him. Baptism is the most important covenant we make in this human life. Marriage is likewise a very important covenant, but still not as important as our relationship with God.
Given this perspective, our recommendation is that people seek baptism prior to marriage. Sometimes, as young people consider marriage, they are sobered by the importance of such a decision and, in the process, realize that baptism is also an important step they want to take. Under such circumstances, a minister will usually counsel people for baptism first and then counsel them for marriage.
When young people marry and later get baptized, we are pleased for them, but we wouldn't recommend this as the best course of action. If someone truly wants to obey God, this will include baptism, and the best chance for a happy marriage is to marry someone who likewise wants to fully obey God. While someone may have good intentions about getting baptized, it is also possible that he or she might not. If you are baptized, I'm sure you will want to marry someone who shares your convictions.
As you suggest, the real key is a person's attitude. Some may get baptized simply to marry another person. If they do, this is unethical, and this is why it is important to talk with a potential mate to see if he or she truly is spiritually compatible. What another person says about God and how he or she acts are usually good indicators of his or her true intentions.